Source: p 132, Philosophy: A Complete Introduction (2012) by Prof. Sharon Kaye MA PhD in Philosophy (U. Toronto)

But how is lying self-contradictory?

[1.] Kant suggests that the very act of speaking presupposes honesty. [2.] That is, why would you make verbal sounds for me to hear unless there was an underlying assumption between us that you were trying to communicate something? When you lie you're not communicating but undermining communication. So your very act negates itself ─ a self-contradiction.

I know that Kant was a deontologist, but appearing to presuppose unreasonably too much, 1 does not convince me. Here is an answer to 2 that rebuts 1: Suppose that most honest people's speaking does evidence the assumption in 2 (that the honest people try to communicate something); but unfortunately, not having studied Logic at university, they may unintentionally commit Logical Fallacies. Then these honest people did not speak honestly, but they did INTEND to speak honestly?


3 Answers 3


I'm not sure I grasp your question or the "rebuttal."

First, "honesty" is not necessarily related to logical fallacies or truth. It is simple consistency between what people say and what they believe, rightly or wrongly.

I would note, as an aside, that the author suggests that Kant's categorical imperative is rooted in the structure of language, which may be a modern interpretation posed by Habbermas and others, but is not exactly how Kant would put it. However, we can stick with the language analogy here, since it makes sense.

Kant assumes that the way to judge moral behavior can be understood logically and abstractly by "universalizing" propositions, as we do when we say to a child: "What if everybody did that?" The case of lying makes this rather obvious. If everybody lied, then "lying itself" would not work, since a lie only works on the supposition that people are not lying. This is, again, readily seen in daily life, where those who constantly lie find themselves no longer believed, Trumpism notwithstanding.

People can, of course, lie, utter fallacies or nonsense, make erroneous statements knowingly or otherwise. But the exceptions prove the rule. Language simply would not function if it were systematically inaccurate and inconsistent with beliefs. Or so Kant claims. While he is correct at one level, the focus on "language" does reveal the shortcomings of this view. For, as we now understand, language can "behave" in many ways, and the half-truths or emotional appeals of ideology or advertising, for example, can be effective without claims to truth. Since Kant's philosophy is not about language per se but about reason, it rests perhaps on firmer, if more abstract, grounds.


While I would tend to agree with Nelson, I'm going to try my own wording on this.

First off, it's not particularly helpful to say "Kant was a deontologist." Kant was Kant, and as far as I know never called himself a deontologist or thought "as a deontologist, I should believe X." Instead Kant saw himself as propounding a critical philosophy in both the domains of theoretical and practical reason.

I take it the Kantian point about lying to be built on a claim about the nature and purpose of communication.

  1. The practice of communication between humans is predicated on the truthful exchange of information in our communication.
  2. Stated positively, this means that acts of communication ought to fulfill this arrangement and convey truth.
  3. Conversely, stated negatively, if we did not think people were in general truthful, then we would not bother communicating with them -- or at a minimum communication would serve a vey different purpose.

Lying only has the effect it does when this definition of communication is in place (I think Kant mistakenly overcommits at some points to a belief that we see nearly all communication as truthful -- though he walks this back a bit in Tugendlehre ("Metaphysical Principles of Justice") by noting that at a party no one expects us to say rude truths).

Thus, to speak at all, presupposes a system of honesty in communication. When we live up to that system and give truth to others, we are properly using our reason. When we do not, we are committing an act that only works because we are parasitically putting lies into a truth-based economy.


I'm not too familiar with this aspect of Kant's philosophy, but I assume that Kant would respond to your question in this manner: if someone intends to be honest, but fails to do so, that failure is not negated by their intentions, and so it remains a lie.

Kant, at least in his ethics, generally stands on the point of the importance lying within the actions rather than the intentions (whether good or bad) behind them, hence his categorical imperatives. If you lie, whether or not you intended not to lie or if the lie served some critical purpose, you are still violating these imperatives, and so, as a consequence, it remains immoral. Therefore, I believe Kant would not agree with your argument here, in that the intentions, to him, are unimportant.

You must log in to answer this question.