A Philosophical Happy Hour considering whether every intentional deception is forbidden, or whether some concealment is not only permitted but required.
What is a lie? And do we often call things “lies” that aren’t, or conflate lies with other forms of concealment or deception?
A difficult and uncomfortable question—but one, perhaps, crucial to ask today. Often, it seems we are in environments where we are not communicating with friends or known persons, but with strangers, potential enemies, or perhaps those whom we simply cannot trust with the truth. How are we to act responsibly, in such situations?
This subtle and nuanced question receives fundamental principles in the Summa Theologiae of St. Thomas Aquinas. St. Thomas places the sin of lying—formally defined as any intent to deceive—in opposition to the virtue of truthfulness; on the surface, this seems like an absolute prohibition against any intentional falsehood. And yet, in his question on the validity of ambushes in a just war, he explicitly permits certain deceptions. This tension opens for us a real question: is every intentional deception morally wrong?
Speaking against Our Convictions
What does it truly mean to lie? Thomas’s treatment of lying, if we read it carefully, shows us a concern with something much deeper than mere factual accuracy. What makes a lie to be a lie, that is, is not merely that it fails to signify what is the case, but rather that the speaker uses language in a way contrary to what he conceives is true. Language is ordered by nature to the purpose of signifying the truth. To lie, then, is not merely to withhold the factually accurate, but to disorder the very act and faculty of signifying itself.
This distinction helps us to see that one need not say everything one knows. Silence and reservation, that is, are not identical with lying. But where exactly does the line fall? Can we only hold back? Can one speak in a way that is technically true but meant to mislead? At what point does reservation become corruption? Can we use outright falsehoods for the sake of the good and the true? These are not merely questions of casuistry but bear directly upon the nature of truth and its role in human virtue.
War, Stratagems, and Required Concealment
Thomas’s discussion of ambushes suggests that concealment need not be immoral. Not every truth must be disclosed to an opponent—or perhaps others, as well—especially where disclosure would directly aid injustice. In such a case, by hiding something we may serve the pursuit of justice. This seems easy enough to grant in war—on, at least, a practical level. But the principle quickly becomes harder to handle once brought back into ordinary life and into the digital re-structuring of social relationality.
That is, let us ask: what is an ambush, morally considered? Only the withholding of information? Or does it intentionally produce false belief in another? If the latter, then how is it distinguished from deception in the ordinary sense? And if deception is sometimes permitted, does that permission extend beyond war into diplomacy, self-protection, law, or interpersonal conflict? Thomas gives us enough to sharpen the problem, but not enough to remove our frequent confrontations with such difficulties in our personal lives—or in the increasingly-complex social and political environment of the digital age.
Mental Reservation—Prudence or Deception?
It is here that the question of mental reservation becomes especially interesting. One may, it is sometimes claimed, attempt to preserve truthfulness by saying words that admit of a true sense inwardly retained, even while the hearer takes them otherwise. But does this genuinely preserve the integrity of language and the moral imperative to use it for the truth?
Join us this Wednesday (25 March 2026, from 5:45-7:15+ pm ET)—no ambushes waiting for anyone! though you may want to read the two selections of St. Thomas (q.110, q.40, a.3)—as we take up these and related questions:
- What distinguishes lying from concealment?
- Does another person always have a right to the truth he asks for?
- Is producing false belief in another always wrong, or only doing so through intentionally misleading assertion?
- Can mental reservation preserve the moral integrity of speech?
- What distinguishes a prudent act of concealment from an unjust use of language?
philosophical happy hour
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Come join us for drinks (adult or otherwise) and a meaningful conversation. Open to the public! Held every Wednesday from 5:45–7:15pm ET.
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