announced the judgment of the Court and an opinion in which Mr. Justice Harlan, Mr. Justice Stewart, and Mr. Justice Blackmun join.
This appeal presents important constitutional questions as to federal aid for church-related colleges and universities under Title I of the Higher Education Facilities Act of 1963, 77 Stat. 364, as amended, 20 U. S. C. §§ 711-721 (1964 ed. and Supp. V), which provides construction grants for buildings and facilities used *675exclusively for secular educational, purposes. We must determine first whether, the Act authorizes aid to such church-related institutions, and, if so, whether the Act violates either the Establishment or Free Exercise Clauses of the First Amendment.
I
The Higher Education Facilities Act was passed in 1963 in response to a strong nationwide demand for the expansion of college and university facilities to meet the sharply rising number of young people demanding higher education. The Act authorizes federal grants and loans to “institutions of higher education” for the construction of a wide variety of “academic facilities.” But § 751 (a)(2) (1964 ed., Supp. V) expressly excludes
“any facility used or to be used for. sectarian instruction or as a place for religious worship, or . . . any facility which ... is used or to be used primarily in connection with any part of the program of a school or department of divinity . . . .”
The Act is administered by the United States Commissioner of Education. He advises colleges and universities applying for funds that under the Act no part of the project may be used for sectarian instruction, religious worship, or the programs of a divinity school. The Commissioner requires applicants to provide assurances that these restrictions will be respected. The United States retains a 20-year interest in any facility constructed with Title I funds. If, during this period, the recipient violates the statutory conditions, the United States is entitled to recover an amount equal to the proportion of its present value that the federal grant bore to the. original cost of the facility. During the 20-year period, the statutory restrictions are enforced by the Office of Education primarily by way of on-site inspections.
*676Appellants are citizens and taxpayers of the United States and residents of Connecticut. They brought this suit for injunctive relief against the officials who administer the Act. Four church-related colleges and universities in Connecticut receiving federal construction grants under Title I were also named as defendants. Federal funds were used for five projects at these four institutions: (1) a library building at Sacred Heart University; (2) a music, drama, and arts building at Annhurst College; (3) a science building at Fairfield University; (4) a library building at Fairfield; and (5) a language laboratory at Albertus Magnus College.
A three-judge federal court was convened under 28 U. S. C. § 2282 and § 2284. Appellants, attempted to show that the four recipient institutions were “sectarian” by introducing evidence of their relations with religious authorities, the content of their curricula, and other in-dicia of their religious character. The sponsorship of these institutions by religious organizations is not disputed. Appellee colleges introduced testimony that they had fully complied with the statutory conditions and that their religious affiliation in no way interfered with the performance of their secular educational functions. The District Court ruled that Title I authorized grants to church-related colleges and universities. It also sustained the constitutionality of the Act, finding that it' had neither the purpose nor the effect of promoting religion. 312 F. Supp. 1191. ‘ We noted probable jurisdiction. 399 U. S. 904 (1970).
II
We are satisfied that Congress intended the Act to include all colleges and universities regardless of any affiliation with or sponsorship by a religious body. Congress defined “institutions of higher education,” which are eligible to receive aid under the Act, in broad and *677inclusive terms. Certain institutions, for example, institutions that are neither public nor nonprofit, are expressly excluded, and the Act expressly prohibits use of the facilities for religious purposes. But the Act makes no reference to religious affiliation or nonaffiliation. Under these circumstances “institutions of higher education” must be taken to include church-related colleges and universities.
This interpretation is fully supported by the legislative history. Although there was extensive debate on the wisdom and constitutionality of aid to institutions affiliated with religious organizations, Congress clearly included them in the program. The sponsors of the Act so stated, 109 Cong. Rec. 19218 (1963) (remarks of Sen. Morse); id., at 14954 (remarks of Rep.- Powell); id., at 14963 (remarks of Rep. Quie), and amendments aimed at the exclusion of church-related institutions were defeated. Id., at 14990-14992, 19496.
Ill
Numerous cases considered by the Court have noted the internal tension in the First Amendment between the Establishment Clause and the Free Exercise Clause. Walz v. Tax Comm’n, 397 U. S. 664 (1970), is the most recent decision seeking to define the boundaries of the neutral area between these two provisions within which the legislature may legitimately act. There, as in other decisions, the Court treated the three main concerns against which the Establishment Clause sought to protect: “sponsorship, financial support, and active involvement of the sovereign in religious activity.” Id., at 668.
Every analysis must begin with the candid acknowledgment that there is no single constitutional caliper that can be used to measure the precise degree to which these three factors are present or absent. Instead, our *678analysis in .this area must begin with a consideration of the cumulative criteria developed over many years and applying to a wide range of governmental action challenged as violative of the Establishment Clause. .
There are always risks in treating criteria discussed by the Court from time to time as “tests” in any limiting sense of that term. Constitutional adjudication does not lend itself to the absolutes of the physical sciences or mathematics. The standards should rather be viewed as guidelines with which to identify instances in which the objectives of the Religion Clauses have been impaired. And, as we have noted in Lemon v. Kurtzman and Earley v. DiCenso, ante, at 612, candor compels the acknowledgment that we can only dimly perceive the boundaries of . permissible government activity in this sensitive area of constitutional adjudication.
Against this background we consider four questions: First, does the Act reflect a secular legislative purpose? Second, is the primary effect of the Act to advance or inhibit religion? Third, does the administration of the Act fostér an excessive government entanglement with religion? Fourth, does the implementation of the Act inhibit the free exercise of religion?
(a)
The stated legislative purpose appears in the preamble where Congress found and declared that
“the security and welfare of the United States require that this and future generations of American youth be assured ample opportunity for the fullest development of their intellectual capacities, and that this opportunity will be jeopardized unless the Nation’s colleges and. universities are encouraged and assisted in their efforts to accommodate rapidly growing numbers of youth who aspire to a higher education.” 20 U. S. C. § 701.
*679This expresses a legitimate secular objective entirely appropriate for governmental action.
The simplistic argument that every form of financial aid to church-sponsored activity violates the Religion Clauses was rejected long ago in Bradfield v. Roberts, 175 U. S. 291 (1899). There a federal construction grant to a hospital operated by a religious order was upheld. Here the Act is challenged on the ground that its primary effect is to aid the religious purposes of church-related colleges and universities. Construction grants surely aid these institutions in the sense that the construction of buildings will assist them to perform their various functions. But bus transportation, textbooks, and tax exemptions all gave aid in the sense that religious bodies would otherwise have been forced to find other sources from which to finance these services. Yet all of these forms of governmental assistance have been upheld. Everson v. Board of Education, 330 U. S. 1 (1947); Board of Education v. Allen, 392 U. S. 236 (1968); Walz v. Tax Comm’n, supra. See also Bradfield v. Roberts, supra. The crucial question is not whether some benefit accrues to a religious institution as a consequence of the legislative program, but whether its principal or primary effect advances religion.
A possibility always exists, of - course, that the legitimate objectives of any law or legislative program may be subverted by conscious design or lax enforcement. There is nothing new in this argument. But judicial concern about these possibilities cannot, standing alone, warrant striking down a statute as unconstitutional.
The Act itself was carefully drafted to ensure that the federally subsidized-facilities would be devoted to the secular and not the religious function of the recipient institutions. It authorizes grants and loans only for academic facilities that will be used for defined secular purposes and expressly prohibits their use for religious *680instruction, training, or worship. These restrictions have been enforced in the Act’s actual administration, and the record shows that some church-related institutions have been required to disgorge benefits for failure to obey them.
Finally, this record fully supports the findings of the District Court that none of the four church-related institutions in this case has violated the statutory restrictions. The institutions presented evidence that there had been no religious services or worship in the federally financed facilities, that there are no religious symbols or plaques in or on them, and that they had been used solely for nonreligious purposes. On this record, therefore, these buildings are indistinguishable from a typical state university facility. Appellants presented no evi-. dence to the contrary.
Appellants instead rely on the argument that government may not subsidize any activities of an institution of higher learning that in some of its programs teaches religious doctrines. This argument rests on Everson where the majority stated that the Establishment Clause barred any “tax . . . levied to support any religious . . . institutions . . . whatever form they may adopt to teach or practice religion.” 330 U. S., at 16. In Allen, however, it was recognized that the Court had fashioned criteria under which an analysis of a statute’s purpose and effect was determinative as to whether religion was being advanced by government action. 392 U. S., at 243; Abington School District v. Schempp, 374 U. S. 203, 222 (1963).
Under this concept appellants’ position depends on the validity of the proposition that religion so permeates the secular education provided by church-related colleges and universities that their religious and secular educational functions are in fact inseparable. The argument that- government grants would thus inevitably advance *681■religion did not escape the notice of Congress. It was carefully and thoughtfully debated, 109 Cong. Rec. 19474-19475, but was found unpersuasive. It was also considered by this Court in Alien. There the Court refused to assume that religiosity in parochial elementary and secondary schools necessarily permeates thé secular education that they provide.
This record, similarly, provides no basis for any such assumption here. Two of the five federally financed buildings involved in this case are libraries. The District Court found that no classes had been conducted in either of these facilities and that no restrictions were imposed by the institutions on the books that they acquired. There is no evidence to the contrary. The third building was a language laboratory at Albertus Magnus College. The evidence showed that this facility was used solely to assist students with their pronunciation in modern foreign languages — a use which would seem peculiarly unrelated and unadaptable to religious indoctrination. Federal grants were also used to build a science building at Fairfield University and a music, drama, and arts building at Annhurst College.
There is no evidence that religion seeps into the use of any of these facilities. Indeed, the parties stipulated in the District Court. that courses at these institutions are taught according to the academic requirements intrinsic to the subject matter and the individual teacher’s concept of professional standards. Although appellants introduced several institutional documents that stated certain religious restrictions on what could be taught, other evidence showed that, these restrictions were not in fact enforced and that the schools were characterized by an atmosphere of academic freedom rather than religious indoctrination. All four institutions, for'example, subscribe to the 1940 Statement of Principles on Aca*682demic Freedom , and Tenure endorsed by the American Association of University Professors and the Association of American Colleges.
Rather than focus on the four defendant colleges and universities involved in this case, however, appellants seek to shift our attention to a “composite profile” that they have constructed of the “typical sectarian” institution of higher education. We are told that such a “composite” institution imposes religious restrictions on admissions, requires attendance at religious activities, compels obedience to the doctrines and dogmas of the faith, requires instruction in theology and doctrine, and does everything it can to propagate a particular religion. Perhapg some church-related schools fit the pattern that appellants describe. Indeed, some colleges have been declared ineligible for aid by the authorities that administer the Act. But appellants do not contend that these four institutions fall within this category. Individual projects can be properly evaluated if and when challenges arise with respect to particular recipients and some evidence is' then presented to show that the institution does in fact possess these characteristics. We cannot, however, strike down an Act of Congress on the basis of a hypothetical “profile.”
(b)
Although we reject appellants’ broad constitutional arguments we do perceive an aspect in which the statute’s enforcement provisions are inadequate to ensure that the impact of the federal aid will not advance religion. If a recipient institution violates any of the statutory restrictions on the use of a federally financed facility, § 754 (b)(2) permits the Government to recover an amount equal to the proportion of the facility’s present value that the federal grant bore to its original cost.
*683This remedy, however, is available to the Government only if the statutory conditions are violated “within twenty years after completion of construction.” This 20-year period is termed by the statute as “the period of Federal interest” and reflects Congress’ finding that after 20 years “the public benefit accruing to the United States” from the use of the federally financed facility “will equal or exceed in value” the amount of the federal grant. 20 U. S. C. § 754 (a).
Under § 754 (b)(2), therefore, a recipient institution’s obligation not to use the facility for sectarian instruction or religious worship would appear to expire at the end of 20 years. We note, for example, that under § 718 (b) (7) (C) (1964 ed., Supp. V), an institution, applying for a federal grant is only required to provide assurances that the facility will not be used for sectarian instruction or religious worship “during at least the period of the Federal interest therein (as defined in section 754 of this title).”
Limiting the prohibition for religious use of the structure to 20 years obviously opens the facility to use for any purpose at the end of that period. It cannot be assumed that a substantial structure has no value after that period and hence the unrestricted-use of a valuable property is in effect a contribution of some value to a religious body. Congress did not base the 20-year provision on any contrary conclusion. If, at the end of 20 years, the building is, for example, converted into a chapel or otherwise used to promote religious interests, the original federal grant will in part have the effect of advancing religion.
To this extent the Act therefore trespasses on the Religion Clauses. The restrictive obligations of a recipient institution under § 751 (a) (2) cannot, compatibly with the Religion Clauses, expire while the building has substantial value. This circumstance does not require us to *684invalidate the- entiré Act, however. “The cardinal principle of statutory construction is to save and not to destroy.” NLRB v. Jones & Laughlin Steel Corp., 301 U. S. 1, 30 (1937). In Champlin Rfg. Co. v. Commission, 286 U. S. 210, 234 (1932), the Court noted
“The unconstitutionality of a part of an Act does not necessarily defeat . . . the validity of its remaining provisions. Unless, it is evident that the legislature would not have enacted those provisions which are within its power, independently of that which is not, the invalid part may be dropped if what is left is fully operative as a law.”
Nor does the absence of ah express severability provision in the Act dictate the demise of the entire statute. E. g., United States v. Jackson, 390 U. S. 570, 585 n. 27 (1968).
We have, found nothing in the statute or its objectives intimating that Congress considered the 20-year provision essential to the statutory program as a whole. In view of the broad and important goals that Congress intended this legislation to serve, there is no basis for assuming that the Act would have failed .of passage without this provision; nor will its excision impair either the operation or administration of the Act in any significant respect.1
IV
We next turn to the question of whether excessive entanglements characterize the Relationship between government and church under the Act. Walz v. Tax Comm’n, supra, at 674-676. Our decision today in *685Lemon v. Kurtzman and Robinson v. DiCenso has discussed' and applied this independent measure of constitutionality under the Religion Clauses. There we concluded that excessive entanglements between government and religion were fostered by Pennsylvania and Rhode Island statutory programs under which state aid was provided to parochial elementary and secondary schools. Here, however, three factors substantially diminish the extent and the potential danger of the entanglement.
In DiCenso the District Court found that the parochial schools in Rhode Island were “an integral part of the religious mission of the Catholic Church.” There, the record fully supported the conclusion that the inculcation of religious values was a substantial if not the dominant purpose of the institutions. The Pennsylvania case was decided on the pleadings, and hence we accepted as true the allegations that the parochial schools in that State shared the same characteristics.
Appellants’ complaint here contains similar allegations. But they were denied by the answers, and there was extensive evidence introduced on the subject. Although the District Court made no findings with respect, to the religious character of the four institutions of higher learning, we are not required to accept the allegations as true under these circumstances, particularly where, as here, appellants themselves do not contend that these four institutions are “sectarian.”
There are generally significant differences between the religious aspects of church-related institutions of higher learning and parochial elementary and secondary schools.2 The “affirmative if not dominant policy” of the instruction in pre-college church schools is “to assure future *686adherents to a particular faith by having control of their total education at an early age.” Walz v. Tax Comm’n, supra, at 671.3 There is substance to the contention that college students are less impressionable and less susceptible to religious indoctrination.4 Common observation would seem to support that view, and Congress may well have entertained it. The skepticism of the college student is not an inconsiderable barrier to any attempt or tendency to. subvert the congressional objectives and limitations. Furthermore, by their very nature, college and postgraduate courses tend to limit the opportunities for sectarian influence by virtue of their own internal disciplines. Many church-related colleges and universities are characterized by a high degree of academic freedom 5 and seek to evoke free and critical responses from their students.
The record here would not support a conclusion that any of these four institutions departed from this general pattern. All four schools are governed by Catholic religious organizations, and the faculties and student bodies at each are predominantly Catholic. Nevertheless, the evidence shows that non-Catholics were admitted as students and given faculty appointments.' Not one of these four institutions requires its students to attend religious services. Although all four schools require their students to take theology courses, the parties stipulated that .these courses are taught according to the academic requirements of the subject matter and the teacher’s concept of professional standards. The parties also stipulated that the courses covered a range of human religious *687experiences and are not limited to courses about the Roman Catholic religion. The schools introduced evidence that they made no attempt to indoctrinate students or to proselytize. Indeed, some of the required theology courses at Albertus Magnus and Sacred Heart are taught by rabbis. Finally, as we have noted, these four schools subscribe to a well-established set of principles of academic freedom, and nothing in this record shows that these principles are not in fact followed. In short, the . evidencé shows institutions. with admittedly religious functions but whose predominant higher education mission is to provide their students with a secular education.
Since religious indoctrination is not “a substantial purpose or activity of these church-related colleges and universities, there is less likelihood than in primary and secondary schools that religion will permeate the area of secular education. This reduces the risk that government aid will in fact serve to support religious activities. Correspondingly, the necessity for intensive government surveillance is diminished and the resulting entanglements between government and religion lessened. Such inspection as may be necessary to ascertain that the facilities are devoted to secular education is minimal and indeed hardly more than the inspections that States impose over all private schools within the reach of compulsory education laws.
The entanglement between church and state is also lessened here by the nonideological character of the aid that the Government provides. Our cases from Everson to Allen have permitted church-related schools to receive government aid in the form of secular, neutral, or non-ideological services, facilities, or materials that are supplied to all students regardless of the affiliation of the school that they attend. In Lemon and DiCenso, however, the state programs subsidized teachers, either directly or indirectly. Since teachers are not necessarily *688religiously neutral, greater governmental surveillance would be required to guarantee that state salary aid would not in fact subsidize religious instruction. There we found the resulting entanglement excessive. Here, on the other hand, the. Government provides facilities that are. themselves religiously neutral. The risks of Government aid to religion and the corresponding need for surveillance are therefore reduced.
Finally, government entanglements with religion are reduced by the circumstance that, unlike the direct and continuing payments under the Pennsylvania program, and all the incidents of regulation and surveillance, the Government aid here is a one-time, single-purpose construction grant. There are no continuing financial relationships or dependencies, no annual audits, and no government analysis of an institution’s expenditures on secular as distinguished from religious activities. Inspection as to use is a minimal contact.
No one of these three factors standing alone is necessarily controlling; cumulatively all of them shape a narrow and limited relationship with government which involves fewer and less significant contacts than the two state schemes beipre us in Lemon and DiCenso. The' relationship therefore has less potential for realizing the substantive evils against which the Religion Clauses were intended to protect.
We think that cumulatively these three factors also substantially lessen the potential for divisive religious fragmentation in the'political arena. This conclusion is admittedly difficult to document, but neither have appellants pointed to any continuing religious aggravation on this matter in the political processes. Possibly this can be explained by the character, and diversity of the recipient colleges and universities and the absence of any intimate continuing relationship or dependency between government and religiously affiliated institutions. The *689potential for divisiveness inherent in the essentially local problems of primary and secondary schools is significantly less with respect to a college or university whose student constituency is not local but diverse and widely dispersed.
V
Finally, we must consider whether the implementation of the Act inhibits the free exercise of religion in violation of the First. Amendment. Appellants claim that the Free Exercise Clause is violated because they are compelled to pay taxes, the proceeds of which in part finance grants under the Act. Appellants, however, are unable to identify any coercion directed at the practice or exercise of their religious beliefs. Board of Education v. Allen, supra, at 248-249. Their share of the cost of the grants under the Act is not fundamentally distinguishable from the impact of the tax exemption sustained in Walz or the provision of textbooks upheld in Allen.
We conclude that the Act does not violate the Religion Clauses of the First Amendment. except that part of § 754 (b) (2) providing a 20-year limitation on the religious use restrictions contained in § 751 (a)(2). We remand to the District Court with directions to. enter a judgment consistent with this opinion.
Vacated and remanded.
[For separate opinion of Mr. Justice Brennan, see ante, p. 642.]
[For opinion of Mr. Justice White, concurring in the judgment, see ante, p. .66T.]
We note that the Commissioner of Education apparently includes no time limitation on the assurances that applicants are required to give with -respect to the use of the facilities for sectarian instruction or religious worship. . Compare § 3 (B) (3) with § 3 (C) of part P of the Application Form, App. 87.
See Freund, Comment, Public Aid to Parochial Schools, 82 Harv. L. Rev. 1680, 1691 (1869).
E. g., J. Fichter, Parochial School: A Sociological Study 77-108 (1958); Giannella, Religious Liberty, Nonestablishment, and Doctrinal Development, pt. II, The Nonestablishment Principle, 81 Harv. L. Rev. 513, 574 (1968).
Giannella, supra, n. 3, at 583.
M. Pattillo & D. Mackenzie, Church-Sponsored Higher Education in the United States 96, 167, 204 (1966).