(After stating the foregoing facts.) There is but one question presented by the record in this ease. Is a county liable as any other individual would be for the payment of interest upon a valid obligation of this municipal subdivision? Or, to state the question in another form, is there any reason why the provisions of § 3434 of the Civil Code of 1910 should rest less heavily upon either the State or any subdivision of the government than it should lie upon an individual? The writer has already expressed his view upon this subject in the case of Citizens Bank of Moultrie v. Rockdale County, 156 Ga. 500 (119 S. E. 322), and given his conscientious opinion that common honesty and good morals apply as much to any branch or subdivision of the government as to private individuals. It is practically conceded in this case that the principal of the debt here involved was a valid obligation of the County of DeKalb. Of course this court cannot assume that to be the law merely.from the fact that in the particular case the county might be estopped by reason of its conduct. But we think that it is perfectly well settled that the interest is as much a part of any debt as is the principal. Epping v. Columbus, 117 Ga. 263, 276 (43 S. E. 803); Park v. Candler, 114 Ga. 466 (40 S. E. 523). The interest follows the principal and is in the same classification; and if the principal is a valid obligation, then necessarily that portion of the debt usually denominated as interest must likewise be valid and binding.
We are requested (if it should be deemed necessary) to review and overrule the previous decisions of this court in the cases of Lettice v. American National Bank, 133 Ga. 874 (67 S. E. 187), First National Bank of Rome v. Owens, 147 Ga. 599 (95 S. E. 2), and Tift & Peed Grocery Co. v. Worth County, 150 Ga. 319 (103 S. E. 465). For the preservation of orderly procedure and in order that there may be uniformity of decisions, the doctrine of stare decisis is entitled to due observance, as recognized by all courts; and yet if the cases cited ought to be overruled, so far as the writer is concerned, we would not hesitate to overrule them. It is true that the experience of ages has established that the rule of stare decisis within reasonable limitations is a most salutary guide, — at once the compass and the (steering-wheel) rudder of the pilot whose duty it is to guide the ship of law in the safest channels and away from rocks and reefs, and thus mark the only *405safe passageway for all others, — whether they “go down to sea in ships” of literature or commerce, and whether the passengers be absorbed in harassing business or only idly intent on luxurious pleasure. All citizens are mariners on the sea of life. The ships of law cannot pursue a zigzag course without imperiling the safety of all mariners, for they must follow the course defined; and ordinary seamen, lacking both the skill and the authority of the pilots, have the right to expect safety for themselves and cargo as long as they follow closely in the wake of their pilot in the charted channel. In numbers of decisions of this court the rule of stare decisis has been upheld and applied (and especially on the ground of public policy, where large numbers of transactions covering a long period of years would probably be disturbed or vitiated, and the rights of those who had followed the law as authoritatively expounded would be adversely affected or destroyed by a different exposition). This is one reason why the rule of stare decisis must ordinarily be applied and strictly followed. However, as said by Chief Justice Bleckley in the ease of City of Atlanta v. First Pres. Church, 86 Ga. 730, 733 (13 S. E. 252, 12 L. R. A. 852), “Courts, like individuals, but with more caution and deliberation, must sometimes reconsider what has already been carefully considered, and rectify their own mistakes. If this is to be done in. any case, it would seem to be a case like the present, where a change of decision would uproot no transaction founded on the prior decision, and where the effect in the particular controversy at the bar would be simply to leave the parties where they had placed themselves by doing aright what one of them now seeks to have undone.” However, after a careful examination of the previous decisions of this court, the question in this case does not appear to have ever been distinctly adjudicated, and the answer to the question, in our opinion, is free from difficulty.
The decisions in the Lettice and the First National Bank eases, supra, are mere headnotes, and in the case last mentioned the opinion was rendered by only five Justices. Therefore it would not be necessary to overrule that case. Besides this, in the ease of State v. Speer, 33 Ga. Supp. 93, it was distinctly held by this court that counties in this State are liable for interest upon their debts. This is the oldest decision of this court upon this question, and under ordinary juridical rules must stand as authority until *406overruled and reversed. If it be said that this decision was prior to the adoption of the constitution of 1877, it can be replied that there is nothing in the constitution of 1877 which abrogates or supplants the decision of this court in the Speer case.
We think it unnecessary to overrule any one of the cases referred to, because in our opinion there is nothing in either one of them which requires the court to disregard the ruling in State v. Speer, which is the oldest case. The holding in the Leitice case amounts to nothing more than a ruling that interest cannot be collected on a debt when the principal represents an invalid obligation. The ruling in that case is sound on principle and the authorities above cited, to the effect that the interest follows the principal and with its accretion gradually becomes a part of the debt. Of course an invalid debt cannot produce valid interest. Certainly nothing said in that case concerns the proposition where the question is raised that interest cannot be collected upon even a valid debt. In the case of First National Bank v. Owens, supra, which is based entirely upon the Leitice case, and where, as in the case at bar, the principal had been paid and payment of the interest only was refused, the court, we think mistakenly, followed the decision in the Leitice case, which was really based entirely upon the fact that the original debt was invalid. The First National Bank case, however, as previously stated, should not be binding, because it is the judgment of only five Justices, and not the opinion of a full bench of six.
In Tift & Peed Grocery Co. v. Worth County, supra, the decision is based upon the principle that the interest partakes of the nature of the principal, and the court dwells upon the term “new debt,” quoting from the decision in the case of Park v. Candler, supra. It cannot be held that interest upon an existing debt is a new debt, for it is simply a consequence of ah old debt already existing (Epping v. Columbus, 117 Ga. 263, 276, supra). And it can safely be said that every liability which a county may legally incur without violating the constitutional prohibition against the creation of a debt may legally bear interest, and that such interest accruing upon such principal liability will not be obnoxious to the constitutional prohibition against the creation or incurring of a new debt. So we are of the opinion that nothing ruled in any of the three cases cited prevents us from now deciding that inter*407est upon a valid debt of a county is as binding as the principal and can be collected if the principal is collectible.
On July 24, 1920, the General Assembly passed an act (Acts 1920, p. 65) expressly providing that all county warrants lawfully issued in the future should bear interest at the legal rate. Of course this act is in no way binding upon this court, since the obligation upon which the alleged past-due interest is sought to be recovered in the present case antedated that act. But the enactment of this law may be considered as indicating the understanding of the General Assembly as to the true law and as a reaffirmation of the doctrine stated in the Speer case, supra, and in view of this expression of the opinion of the legislature, it is our opinion that this court should be compelled and forced to the conclusion that the constitution forbids the payment of interest in a case like this, or else resolve any doubts upon that subject in favor of its constitutionality. “Mere doubt as to the constitutionality of a particular enactment settles its validity.” Heard v. State, 113 Ga. 444, 447 (39 S. E. 118); Cone v. American Surety Co., 154 Ga. 849 (115 S. E. 481).
We think the trial judge erred in refusing to issue.the mandamus prayed for; and accordingly the judgment of the lower court must be Reversed.
All the Justices concur, except