This is a will' contest, brought by testator Corwin E. Porter’s natural children, Harold D. Porter, James E. Porter and Donna C. Bingham. Defendant Wayne E. Nelson1 is one of the named beneficiaries under the will.
Pertinent parts of the contested will follow:
ARTICLE I
In the event my wife, Sena C. Porter, survives me, I hereby give all of my property, real and personal, to her absolutely.
ARTICLE II
If my wife, Sena C. Porter, shall predecease me, then and in that event I give all my property, real and personal, to my son-in-law,2 Wayne E. Nelson, or his heirs, share and share alike.
ARTICLE III
In the event that my son-in-law, Wayne E. Nelson, shall predecease me and leave no heirs, then and in that event I give all my property, real and personal to the Ramsey Memorial Home of Des Moines, Iowa, absolutely.
ARTICLE VI
I am aware that this Will neglects to mention my children, Harold, James and Donna, and it is my desire to leave my estate as set out above and not to my children.
Testator executed the contested will on December 14, 1973. On December 7, 1976, the marriage between testator and Sena was dissolved by decree. Without having revoked or modified his will, testator died on July 1, 1977. Both Sena and defendant survived him.
After the will was filed for probate, plaintiffs filed a petition to have the will set aside and the estate pass by intestate succession. They alleged that the dissolution in effect revoked all provisions in the will in favor of Sena because of the operation of section 633.271, The Code. That section provides, in part: “If after making a will the testator is divorced or the marriage is dissolved, all provisions in the will in favor of the testator’s spouse are thereby revoked.”
*652The' petition also stated that the bequest to defendant must fail either because it should be considered a gift “in favor of” Sena or because it was conditioned upon an event which had not occurred, that is, Sena’s predeceasing testator. Finally, it alleged that at the time of executing the will testator was of unsound mind and unduly influenced by Sena.
Subsequently, plaintiffs filed an application for an adjudication of law points under Iowa R.Civ.P. 105, asking whether defendant was entitled to take under the terms of the will.3 Trial court ruled that the gift over to defendant failed and that the estate passed by intestacy. Its rationale was that the death of the spouse prior to that of testator was a necessary condition precedent to effectuation of the gift over.
Defendant was granted permission to appeal that ruling in advance of judgment, pursuant to Iowa R.App.P. 2. The court of appeals reversed, holding that in this case testator’s estate passed as if the former spouse had failed to survive testator. That court reasoned that testator’s unmistakable intent was to disinherit his three natural children and leave the estate to others. This was evidenced, it said, by Article III, which named an alternative contingent beneficiary other than testator’s natural children, and by Article VI, which specifically disinherited his natural children. We subsequently granted plaintiffs’ application for further review of the decision of the court of appeals and now affirm that decision.
This appeal presents a narrow issue of first impression: the proper construction of a gift over made contingent upon the death of the spouse when the spouse, who is divorced from the testator after execution of the will, survives the testator but is barred from taking under the will by operation of section 633.271.
Because the answer to this question lies in a determination of the testator’s intent, which is the guiding light in will interpretation, Covert v. Sebern, 73 Iowa 564, 566-67, 35 N.W. 636, 638 (1887), no blanket rule of construction is appropriate. While technical rules of construction may be employed if the will is ambiguous or testator’s intent is for any other reason uncertain, In re Estate of Kalouse, 282 N.W.2d 98, 100 (Iowa 1979), such is not the case here. Consequently, we need not attempt to now formulate, by way of dictum, a rule of construction for cases in which this issue is involved but the testator’s intent is not clearly evidenced.
The testator’s intent is to be determined by examination of the whole will. As stated in Elkader Production Credit Association v. Eulberg, 251 N.W.2d 234, 237-38 (Iowa 1977),
[A] testator’s intent is not to be ascertained from a single part or paragraph o[f] his or her will. That means the instrument must be read and considered as a whole, each part in connection with every other part and with the entire will, with each part given meaning and effect if possible.
Concomitant to an examination of the whole will and also helpful in gleaning the testator’s intent is an examination of the scheme of distribution. Additionally relevant to ascertaining the testator’s intent are the circumstances surrounding him at the time he made his will and the existing facts. See, e. g., In re Estate of Lamp, 172 N.W.2d 254, 257 (Iowa 1969).
Applying these principles of interpretation to the will before us, we conclude that testator intended that his estate should devolve upon defendant if testator’s former spouse for any reason could not take under the will. Any indefiniteness regarding testator’s intent in including the condition of his wife’s predeceasing him in his will is *653clarified by the remaining provisions of the will. The whole will evinces a scheme of distribution to prefer testator’s wife first, his stepson second and the Ramsey Memorial Home third. Testator’s natural children not only were excluded inferentially by the fact that testator specified three alternative beneficiaries in preference to them but also explicitly in Article VI, which provides, “it is my desire to leave my estate as set out above and not to my children.” To interpret the condition of his wife’s predeceasing him strictly would defy the remaining provisions of the will and testator’s obvious plan of distribution. To interpret it rather as a means of indicating his order of preference for beneficiaries and of preventing lapse of his bequests gives harmonious meaning to all provisions of the will.
Moreover, this court has previously favored the interpretation of conditions which avoids forfeiture and permits the bequests. See In re Estate of Anderson, 244 Iowa 325, 331-32, 56 N.W.2d 913, 917 (1953); In re Estate of Nugen, 223 Iowa 428, 435, 272 N.W. 638, 642 (1937) (“As between contingent and vested estates, conditions precedent and conditions subsequent, forfeitable rights and nonforfeitable rights, the courts always incline to the latter whenever it can fairly be done without violence to the language of the instrument under which the claims of the parties are asserted.”); 5 W. Bowe & D. Parker, Page on the Law of Wills § 44.3, at 401 (rev. 1962) (“[W]here there is a condition precedent the happening of which would create an estate without divesting another it may be construed liberally in favor of the beneficiary.”).
Our interpretation of the will's condition in this case is also consistent with other principles of construction recognized by previous decisions of this court. One is that substantial performance of a condition in a will is sufficient to vest an interest in property if intestacy would result from a more literal interpretation. See, e. g., Livingston v. Lenox College, 192 Iowa 579, 185 N.W. 122 (1921) (condition that devise vest if college raise $25,000 within certain time period fulfilled by obtaining subscriptions for that amount, payable at a time later than the prescribed period). Another principle is that the time of death required to meet a condition to a bequest of another beneficiary’s death is normally construed as being prior to the testator’s death. See, e. g., Shoberg v. Rock, 230 Iowa 807, 810, 298 N.W. 838, 839 (1941). This may be explained by a preference for interpreting the survivorship clause as a direction for substitution to prevent lapse rather than as a condition. 5 W. Bowe & D. Parker, supra § 44.14, at 430. Yet another, and more general, principle is that a will must be read, if possible, so as to avoid intestacy. See, e. g., In re Estate of Lamp, 172 N.W.2d at 257, 258-59.
Our conclusion is also supported by the majority of decisions from other jurisdictions which have considered the issue. Most of those jurisdictions also base their interpretation of similar will provisions on a determination of the testator’s intent. See, e. g., In re Estate of Fredericks, 311 So.2d 376, 379 (Fla.Dist.Ct.App.1975); Steele v. Chase, 151 Ind.App. 600, 606-07, 281 N.E.2d 137,140 (1972); Russell v. Estate of Russell, 216 Kan. 730, 734, 534 P.2d 261, 265 (1975); Calloway v. Estate of Gasser, 558 S.W.2d 571, 574-76 (Tex.Civ.App.1977); cf. First Church of Christ, Scientist v. Watson, 286 Ala. 270, 273, 239 So.2d 194, 196 (1970) (presuming spouse’s civil death unless a contrary intention is apparent from the will); In re Estate of Zimmerman, 28 Ill.App.3d 107, 109, 328 N.E.2d 199, 200 (1975); In re Estate of Lampshire, 57 Misc.2d 332, 334, 292 N.Y.S.2d 578, 580-81 (Sur.Ct.1968); In re Estate of McLaughlin, 11 Wash.App. 320, 322-23, 523 P.2d 437, 438-39 (1974) (declaring testator’s intent unexpressed and thus unfathomable as to effect of dissolution upon terms of will). Significantly, in the two eases where the testator had specified in his will that his natural heirs were to receive nothing or a nominal amount, it was held that the testator’s clear intention was to dispose of his property according to his will rather than the laws of intestate succession. See Russell v. Estate of Russell, 216 Kan. 730, 534 P.2d 261 (1975); Peiffer v. Old National Bank & Union Trust Co., *654166 Wash. 1, 6 P.2d 386 (1931). Even wills without an explicit disinheritance clause have been interpreted by the majority of jurisdictions to demonstrate testamentary intent to uphold the gift over. See In re Estate of Fredericks, 311 So.2d 376 (Fla.Dist.Ct.App.1975); Steele v. Chase, 151 Ind. App. 600, 281 N.E.2d 137 (1972); Calloway v. Estate of Gasser, 558 S.W.2d 571 (Tex.Civ.App.1977). But see In re Estate of McLaughlin, 11 Wash.App. at 322, 523 P.2d at 438 (finding dispositive, and the basis for distinguishing Peiffer, the absence of a disinheritance clause). See generally Annot., 74 A.L.R.3d 1108 (1976).
Plaintiffs make a number of arguments on behalf of revoking the gift over to defendant. First, they contend that the will must be construed as written and that in construing a will the question is.not what the testator may have meant, but what the meaning is of the words actually used.
While this court has recognized the importance of the requirement of written expression of the testator’s intent by the above rules, see, e. g., In re Estate of Fairley, 159 N.W.2d 286, 288-91 (Iowa 1968), we have also recognized that in order to give proper respect to the testator’s intent a court may determine that the testator made a gift “by necessary implication” from his will, id. at 289 (quoting dictum from Bankers Trust Co. v. Allen, 257 Iowa 938, 945, 135 N.W.2d 607, 611 (1965)); In re Estate of Loranz, 256 Iowa 818, 820, 128 N.W.2d 224, 225 (1964) (permitting beneficiary of bequest of property “that has not been specifically devised or bequeathed” to receive renounced legacy); In re Estate of Mount, 189 Iowa 279, 285, 178 N.W. 391, 393 (1920) (“A bequest will be implied, as a matter of law, from the direction therein to sell and distribute.”); Vorse v. Vorse, 186 Iowa 1091, 1092-97, 171 N.W. 186, 186-88 (1919) (will bequeathing “entire estate” to two sons and stating testator’s desire that wife be paid “good and reasonable support” implied that sons’ devise was subject to duty to support mother); cf. In re Estate of Spencer, 232 N.W.2d 491, 498 (Iowa 1975) (implied gift theory used when there is a default in the exercise of a special power of appointment). See also In re Estate of Beaver, 206 N.W.2d 692, 696 (Iowa 1973) (in case of impossibility of performance by beneficiary of will, permitting the court to inquire, “not as to what the conveyor actually intended, but as to what his intent would have been had he known of or anticipated the impossibility at the time he imposed the restraint”) (quoting Restatement of Property § 438, Comment c (1944)).
The doctrine of gift by implication has been described more fully by other jurisdictions that have had occasion to apply it. For example, Davis v. Davis, 24 Ohio Misc. 17, 24, 258 N.E.2d 277, 282 (Ct.C.P.1970), explains:
When a testator’s will clearly reveals a general plan or intention as to the disposition of his property, and a situation arises that is not within the express language of the will, such general plan may be regarded as existing but incompletely expressed, and the failure to provide for the situation inadvertent rather than intentional, and a gift may be implied for the purpose of completing the general plan.
Accord, In re Estate of Cummings, 263 Cal.App.2d 661, 666-67, 69 Cal.Rptr. 792, 796 (1968); In re Will of McDowell, 81 N.M. 562, 564, 469 P.2d 711, 713 (1970); In re Estate of D’Alessandro, 55 Misc.2d 909, 911-15, 286 N.Y.S.2d 914, 917-20 (Sur.Ct.1968); In re Estate of Lull, 120 Vt. 195, 200, 138 A.2d 615, 619 (1958). See generally 4 W. Bowe & D. Parker, supra § 30.18; 95 C.J.S. Wills § 595 (1957).
This well-established doctrine is particularly appropriate in situations where the testator bequeaths property in contemplation of one contingency and then another contingency occurs which was not provided for in the will. Depending on the particular facts of the case, the testator’s disposing intent may be implied with regard to the unmentioned contingency. See, e. g., Fay v. Fay, 334 Mass. 311, 319-21, 135 N.E.2d 306, 311-12 (1956); In re Estate of Thall, 18 N.Y.2d 186, 192-94, 273 N.Y.S.2d 33, 36-37, 219 N.E.2d 397, 399 (1966); In re Estate of *655McWilliams, 78 Wis.2d 328, 334-35, 254 N.W.2d 277, 280-81 (1977). See generally 80 Am.Jur.2d Wills §§ 1385, 1390, 1391 (1975). The probability of the implication is usually required to be so strong that a contrary intention cannot be supposed; conjecture will not support an implied gift. See, e. g., Ravenel v. Shipman, 271 N.C. 193, 196, 155 S.E.2d 484, 486-87 (1967); Najvar v. Vasek, 564 S.W.2d 202, 210 (Tex.Civ.App.1978); Seattle-First National Bank v. Tingley, 22 Wash.App. 258, 263, 589 P.2d 811, 814 (1978). This is traditionally referred to as Lord Eldon’s Rule, announced in Wilkinson v. Adam, 35 Eng.Rep. 163, 180 (Ch.1812). Cf. In re Estate of Fairley, 159 N.W.2d at 288-89 (logical speculation on testator’s intent generally insufficient for will construction). But see Clapp, Justice Nathan L. Jacobs — The Doctrine of Probable Intent, 28 Rutgers L.Rev. 251 (1975) (indicating that New Jersey courts are applying less rigorous standard than Lord Eldon’s Rule).
The doctrine of gift by implication is fully applicable here. Testator’s will set forth a complete scheme of distribution, indicating that his intent to bequeath property to defendant extended not only to the contingency accounted for in the will, Sena’s predeceasing testator, but also to the contingency which actually occurred, the dissolution and revocation by law of Sena’s bequest. In view of the whole will, especially the disinheritance clause, a contrary intention cannot be realistically supposed.
Nonetheless, plaintiffs argue that the gift by implication doctrine is inappropriate in this situation, citing Davis v. Davis, 24 Ohio Misc. at 25-26, 258 N.E.2d at 283. The Davis court reasoned that the testator’s general testamentary plan had been grossly distorted by the separation agreement, divorce and revocation by law of the wife’s bequest, thus destroying the basis for a gift by implication.
While Davis is distinguishable because the will there included no clause disinheriting the testator’s heirs, we also believe its rationale is overbroad. There is no reason to assume that in all or even most cases a testator estranged from his spouse will also be estranged from alternative beneficiaries under the will, even if they are relatives of that spouse. The results of other jurisdictions considering the validity of gifts over to testators’ stepchildren are divided. Compare Lamontagne v. Hunter, 341 So.2d 1074 (Fla.Dist.Ct.App.1977), and Russell v. Estate of Russell, 216 Kan. 730, 534 P.2d 261 (1975) (upholding gifts over to stepchildren), with In re Will of Lampshire, 57 Misc.2d 332, 292 N.Y.S.2d 578 (Sur.Ct. 1968), and In re Estate of McLaughlin, 11 Wash.App. 320, 523 P.2d 437 (1974) (revoking gifts over to stepchildren). We concur with the recognition in Steele v. Chase, 151 Ind.App. 600, 607, 281 N.E.2d 137, 140-41 (1972), that “in certain circumstances a relative of a divorced spouse may receive a greater devise than the heirs at law, yet a court may not speculate as to what decedent’s intentions may have been and thus rewrite his will.”
Also, to interpret section 633.-271 as Davis advises would violate the rule that statutes will not be construed as taking away common law rights existing at the time of enactment unless that result is imperatively required. Jansen v. Harmon, 164 N.W.2d 323, 328 (Iowa 1969); see In re Estate of Brown, 139 Iowa 219, 223, 117 N.W. 260, 262 (1908) (prior to statute, no implied revocation of testamentary disposition to prior spouse resulted from divorce). Section 633.271 is directed only toward bequests to the testator’s divorced spouse, not other objects of his bounty as well. Cf. Todora v. Todora, 92 Nev. 566, 568, 554 P.2d 738, 739-40 (1976) (per curiam) (refusing to revoke appointment in will of divorced spouse as executrix under similar state statute).
Next, plaintiffs urge that when construction of a will is required, a construction is favored which most nearly brings the bequest in conformity with laws of descent and distribution. This is a valid rule of construction. See, e. g., Watson v. Manley, 257 Iowa 92, 97, 130 N.W.2d 693, 696 (1964). However, rules of construction *656are subservient to the testator’s written expression for ascertaining his intent. Here, testator clearly indicated that he did not intend his natural heirs to take when he expressly so stated in his will. Such disinheritance clauses are operative where, as in this case, valid disposition is made of testator’s property. Elkader Production Credit Association v. Eulberg, 251 N.W.2d at 238-39; see In re Estate of Lamp, 172 N.W.2d at 259.
Finally, plaintiffs argue that upholding the gift over would violate legislative intent because the legislature did not elect, in section 633.271, to deem the divorced spouse civilly dead, as did Uniform Probate Code § 2-508 and statutes modeled after that provision. See In re Will of Lampshire, 57 Misc.2d at 333-34, 292 N.Y. S.2d at 579-80. We discern no clear legislative intent with regard to this issue.4 Moreover, we do not here attempt to fill the legislative gap with a comprehensive rule of construction. Our decisions will continue to be based on a determination of the testator’s intent, if demonstrable, in each particular case.
Although we affirm the court of appeals’ decision, reversing trial court’s ruling that the gift over fails under the terms of the will, the case must be remanded for trial of plaintiffs’ other grounds for contesting the will: that testator was of unsound mind and unduly influenced in making his will.
DECISION OF COURT OF APPEALS AFFIRMED AND CASE REMANDED.
All Justices concur except REYNOLD-SON, C. J., McGIVERIN, REES and HARRIS, JJ., who dissent.. The original petition also named Sena C. Porter and the Ramsey Memorial Home as defendants and proponents of the will. Subsequently, trial court rendered a default judgment against Sena for failure to comply with an order compelling discovery. Of the two remaining defendants, only Wayne Nelson appealed trial court’s ruling on the motion here at issue.
. Although the will refers to defendant as testator’s son-in-law, he was in fact the son of Sena by a prior marriage and thus testator’s stepson. This misdescription of testator’s relationship to defendant does not invalidate the gift over because the designation by name shows testator’s intent beyond reasonable dispute. See Hollenbeck v. Gray, 185 N.W.2d 767, 770-71 (Iowa 1971); In re Estate of Brown, 139 Iowa 219, 223, 117 N.W. 260, 262 (1908). See also Barnstable v. United States Nat'l Bank, 232 Or. 36, 38-42, 374 P.2d 386, 387-89 (1962) (en banc) (adopted daughter referred to as “foster daughter”).
. Rule 105 was an appropriate vehicle for plaintiffs’ question because it sought a determination of the legal effect of certain uncontro-verted pleadings. See M & W Farm Service Co. v. Callison, 285 N.W.2d 271, 274 (Iowa 1979). The facts settled by the pleadings were the contents of the will, which had been incorporated into the pleadings; that the dissolution occurred at a time subsequent to the making of the will but prior to testator’s death; and that both Sena and defendant survived testator.
. Because § 633.271 was passed by the legislature in 1963, see 60th G.A., ch. 326, § 271, and the UPC was not approved by the National Conference of Commissioners on Uniform State Laws and by the American Bar Association until 1969, Foreward to Uniform Probate Code at III, the UPC provision was not available for consideration by the drafters of § 633.-271. A comment to the original bill, 60th G.A., S.F. 165, § 271, states only that it was adapted from § 53 of the Model Probate Code. •