William Ames
Marrow of Theology 2.21.

Of Telling Truth — Veracity.

1. Justice which affects our neighbour mediately, is veracity and contentment. For by that veracity, our neighbour’s credit or reputation is affected; and by means of some work or action on our part which belongs to some prior commandment.

2. Veracity is a virtue, whereby we are inclined to observe truth in giving testimony (Mat. 23.22; Eph. 4.25; Psa. 15.2).

3. The ninth precept properly handles this telling truth in giving testimony; and not only about those things which chiefly pertain to the fame of our neighbour, for fame pertains to the consideration of that honour which is had in the fifth precept. Nor is it to be put after riches and the profits of this life, which was handled in the eighth commandment (Prov. 22.1). Nor does a testimony, whether true or false, pertain only to the fame of others, but also to their possessions, and life itself (Prov. 14.25).

4. It is also manifest that the words of this precept most directly respect proceeding in judgment (Num. 35.30; Deut. 17.6; 19.15). In these places, many other things are handled besides fame, although they should also be extended to all public, political, and sacred testimonies (1 Cor. 15.15; John 1.7-8, 15, 19, 32, 34).

5. Hence, actions in places of judgment, not only have approval, but also direction from this precept; namely, that judgments should always be grounded on fit testimony (unless there is evidence of the matter which serves to witness), or at least strong and violent (as they call them) presumptions, which are equal to testimonies.

6. The words of a testimony must always be used in the sense they are understood, or are thought to be understood, by those to whom the witnesses endeavour to give credence, without equivocation, doubting, or mental reservation.

7. Truth in a testimony is threefold. 1. When what is said conforms to the thing in hand. 2. When it conforms to the mind of the one who speaks it. 3. When it conforms both to the thing and to the mind.

8. The second truth is that which is most properly looked at in a testimony and in veracity: yet the third is required in those things of which we are either bound or profess to have certain knowledge.

9. This veracity is either in a simple assertion, or in a promise.

10. The truth of an assertion is always necessary thus far: that if we affirm anything, it agrees with the mind and our judgment.

11. Also, an assertion itself is necessary, when either justice or charity may require it of us.

12. Justice requires it in public judgments of the judge, of the plaintiff, of the defendant, of the witness, of the advocate, the notary, and the proctor; and out of judgment, when we are bound to bear witness by some special right.

13. Charity requires this when good comes to our neighbour by it, without equivalent hurt to ourselves or others.

14. The truth of a promise is called fidelity.

15. Fidelity is a virtue, whereby we are inclined to constantly keep our credit given.

16. This fidelity is the foundation of civil Justice, and all agreements and contracts: for a reciprocal promise is a contract.

17. Opposed to the truth of a testimony, is a Lie (Eph. 4.25).

18. A lie is properly a testimony by which one declares other than what is in his heart (Acts 5.3). From this comes that phrase in Scripture of a “double heart” of a man that is a liar (Psa. 12.2).

19. But because what is declared does not consist only in outward words, but chiefly in their sense, the same words which are true in one sense, become a lie in another sense (Mat 26.61).

20. Ironies, fables, jests, also repeating false things and their like, are not lies, because they are not testimonies; and they are not testimonies because they are not confirmed by the credit and authority of the speaker.

21. Although it almost always accompanies a false testimony, an intention to deceive is not the essence of a lie, nor is it required for a lie. For even though one knows that the one with whom he is dealing cannot be deceived by his lie, yet if he intends to affirm what is false, he lies no less than if he hoped to deceive.

22. An intention to hurt indeed increases the mischief of a lie, but it does not make the nature of it a lie: for if a man out of jesting, or a desire to please, or to be officious, confirms by his credit what he knows to be false, it is a lie. It is pernicious of its own nature, if not to others, yet to the author himself — just as it is in those who are given to flattery or boasting, or who are delighted to confirm monstrous fables or fictions to others.

23. An intention to speak what is false is what makes a lie, even if what is spoken is most true.

24. To asseverate what is uncertain, as being certain, is considered a lie, even though we think it is true.

25. Also that secrecy by which one does not speak the truth when justice or charity requires it, partakes of the nature of a lie.

26. But when neither justice nor charity requires us to give testimony, then the truth, or part of it, may be concealed without sin (Jer. 38.27).

27. Lies are more heinous where the testimony is more solemn, as in public judgments (which are chiefly referred to in the ninth precept), sacred matters, and the like (Mat 26.59; 1Cor 15.15).

28. Hence subscriptions, testimonies, or commendatory letters, given against the known truth, are foul lies.

29. That dissembling which consists in deeds or signs, and not in words, is not properly a lie, unless of their own nature, or by some certain appointment, they have the force and use of speech, as in 1 Sam. 20.20-22; Mat 26.49. This is because such non-verbal deeds and signs have no certain and determinate meaning, so as to have the force of a testimony.

30. Therefore such dissembling is sometimes lawful, as in warlike stratagems (Joshua 8).

31. But it is made unlawful when, in respect to its end or manner, it conflicts with religion, Justice, or Charity.

32. To fidelity is opposed perfidy or unfaithfulness.

33. A lie is committed in a promise if there is no intention to do what is promised; unfaithfulness is committed if there is no corresponding endeavour to perform it; therefore a lie and unfaithfulness, may be joined together, and they may also be severed.

34. When a testimony toward our neighbour is confirmed by an oath, then the oath is an adjunct of that testimony: even though in itself it respects God only, yet in this use, it respects our neighbour also.

35. Therefore perjury in such a testimony is directly and immediately a sin against the reverence due to God: but mediately it also violates that Justice which is due to our neighbour.

36. Asseveration is the manner of a testimony by which the sincerity of the witness is declared, and also the certitude of knowledge which he has of the thing witnessed; this is why it is not unfitly called a protestation by some, because it produces witnessing by explication.

37. Therefore, in an asseveration there is no second contesting coming to the former, as there is in an oath, but an illustration of one and the same thing.

38. Nor in a mere asseveration is there any calling upon God, which is essential to an oath.

39. Yet an asseveration is only convenient for graver testimonies; for it is, as it were, a middle degree between a simple testimony and an oath.

40. We must abstain most of all from those asseverations in our common speech, which have some show of an oath.