13 In which proposition these points may well deserve to be questioned: whether such consent is to be accounted as a deed: or whether that is to be called consent which has not approbation: or whether it be approbation, when it is said, “It is expedient to suffer this rather than do that;” and whether the person spoken of did right to burn incense rather than suffer violation of his body; and whether it would be right rather to tell a lie, if that was the alternative proposed, than to burn incense? But if such consent is to be accounted as a deed, then are they murderers who have chosen rather to be put to death than bear false witness, yea, what is worse, they are murderers of themselves. For why, at this rate, should it not be said that they have slain themselves, because they chose that this should be done to them that they might not do what they were urged to do? Or, if it be accounted a worse thing to slay another than himself, what if these terms were offered to a Martyr, that, upon his refusing to bear false witness of Christ and to sacrifice to demons, then, before his eyes, not some other man, but his own father should be put to death; his father entreating him that he would not by his persevering permit that to be done? Is it not manifest, that, upon his remaining steadfast in his purpose of most faithful testimony, they alone would be the murderers who should slay his father, and not he a parricide into the bargain? As therefore, in this case, the man would be no party to this so heinous deed, for choosing, rather than violate his faith by false testimony, that his own father should be put to death by others, (yea, though that father were a sacrilegious person whose soul would be snatched away to punishment;) so the like consent, in the former case, would not make him a party to that so foul disgrace, if he refused to do evil himself, let others do what they might in consequence of his not doing it. For what do such persecutors say, but, “Do evil that we may not?” If the case were so, that our doing evil would make them not to have done it, even then it would not be our duty by doing wickedness ourselves to vote them harmless; but as in fact they are already doing it when they say nothing of the kind, why are they to have us to keep them company in wickedness rather than be vile and noisome by themselves? For that is not to be called consent; seeing that we do not approve what they do, always wishing that they would not, and, as much as in us lies, hindering them that they should not do it, and, when it is done, not only not committing it with them, but with all possible detestation condemning the same.
14. “How,” do you say, “is it not his doing as well as theirs, when they would not do this, if he would do that?” Why, at this rate we go housebreaking with house-breakers, because if we did not shut the door, they would not break it open: and we go and murder with highwaymen, if it chance we know that they are going to do it, because if we killed them out of hand, they would not kill others. Or, if a person confess to us that he is going to commit a parricide, we commit it along with him, if, being able, we do not slay him before he can do the deed when we cannot in some other way prevent or thwart him. For it may be said, word for word as before, “You have done it as well as he; for he had not done this, had you done that.” With my good will, neither ill should be done; but only the one was in my power, and I could take care that this should not be done; the other rested with another, and when by my good advice I could not quench the purpose, I was not bound by my evil deed to thwart the doing. It is therefore no approving of a sinner, that one refuses to sin for him; and neither the one nor the other is liked by him who would that neither were done; but in that which pertains to him, he has the power to do it or not, and with that he perpetrates it not; in that which pertains to another, he has only the will to wish it or not, and with that he condemns. And therefore, on their offering those terms, and saying, “If you burn not incense, this shall you suffer;” if he should answer, “For me, I choose neither, I detest both, I consent unto you in none of these things:” in uttering these and the like words, which certainly, because they would be true, would afford them no consent no approbation of his, let him suffer at their hands what he might, to his account would be set down the receipt of wrongs, to theirs the commission of sins. “Ought he then,” it may be asked, “to suffer his person to be violated rather than burn incense?” If the question be what he ought, he ought to do neither. For should I say that he ought to do any of these things, I shall approve this or that, whereas I reprobate both. But if the question be, which of these he ought in preference to avoid, not being able to avoid both but able to avoid one or other: I will answer, “His own sin, rather than another's; and rather a lighter sin being his own, than a heavier being another's.” For, reserving the point for more diligent inquiry, and granting in the mean while that violation of the person is worse than burning incense, yet the latter is his own, the former another's deed, although he had it done to him; now, whose the deed, his the sin. For though murder is a greater sin than stealing, yet it is worse to steal than to suffer murder. Therefore, if it were proposed to any man that, if he would not steal he should be killed, that is, murder should be committed upon him; being he could not avoid both, he would prefer to avoid that which would be his own sin, rather than that which would be another's. Nor would the latter become his act for being committed upon him, and because he might avoid it if he would commit a sin of his own.
Source: On Lying (New Advent)