When we communicate truthfully we describe a state of the world as we know it, or have normative reasons to believe, with the intention to make someone else believe that the relevant state is a part of the world as we know it. This definition is certainly not exhaustive, it does not, for example, cover ‘abstract truths’, but in relation to facts about the world we are in it is uncontroversial. Conversely, there is no universally accepted definition of what it means to lie to others.

It is possible to characterise lying (or communicating untruthfully) as follows: (D1) When we lie, or when we believe that we are lying, we make a statement with the intention to deceive someone else (Davidson 1980), where ‘to deceive’ means that person X causes Y to believe P (or persist in believing P), where P is false and X does not believe that P is true (Carson 2010, 50). This hybrid definition is unnecessarily convoluted since ‘lying’ and ‘deception’ are near-synonyms, but more importantly, Davidson’s part is already too broad. The subjective notion of ‘belief’ presupposes the idea of truth that may or may not correspond to the relevant belief. This is reinforced by Carson’s definition of ‘deception’ (cited above). Deception does not make sense in the normative void and therefore cannot be just about beliefs; it is also, and primarily, about the reasons to believe. This normative aspect is rarely elaborated in the literature on lying and deception but is crucial to understanding the logical limits of lying and for developing effective counter-strategies to being deceived.

To better capture the normative aspect of deception I propose the following definition: (D2) When we lie, or when we believe that we are lying, we describe a hypothetical state of the world that we know through experience (or have other normative reasons to believe) that it is not a part of the world, with the intention to make someone else believe that the relevant state is a part of the world. This definition nonetheless equivocates between different possible worlds: the world we know through experience (or have other normative reasons to believe something about) and an alternative world that we do not know through experience (and do not have other normative reasons to believe anything about). To avoid the equivocation fallacy we may explicitly characterise lying in terms of ‘possible worlds’ (Lewis 1986, 5): a exists (or is true) in a possible world W iff a is a part of W. (D3) When we lie, or when we believe that we are lying, we describe a state of a possible world that we do not know through experience (and do not have any other normative reasons to believe) to be a part of the actual world, with the intention to make someone else believe that the relevant state is a part of the actual world. This characterisation implies epistemic vulnerability in the act of lying: a liar does not know and has no normative reasons to believe that a particular state of a possible world is possible, let alone possible in the actual world. No matter how elaborate the lie, a liar is not able to consistently integrate a state of a possible world and the actual world. Possible worlds are essentially isolated (Lewis 1986, 2).

Suppose that Sally is determined to lie convincingly. In order for her description of the state of a possible world (unknown to her through experience) to be convincing to others it would need to be at least possible in the light of experiences of others. Sally must then construct a possible world that in every imaginable respect, apart from the information-content of the lie, corresponds to the world that she and others know through experience and in which her description would be consistent with experiences (or normative reasons) of others. Another way, Sally can lie convincingly only about contingent facts of which no one but herself knows through experience not to be part of the same world. Since the scope of experience of others is uncertain, so is the scope of contingent facts that Sally can convincingly lie about. It follows that Sally can maximise her chances of lying convincingly by narrowing the scope of contingent facts she is lying about, keeping the lie as close to the truth as possible without compromising her strategic aim.

Sally may be aware of this uncertainty and of the associated risk of being found out, and so she may try to maintain plausible deniability in case her lies were refuted by someone else’s experience. Since with every new lie the odds of Sally being found out increase, and given she is determined to lie, she may attempt to control other people’s experiences and normative reasons in a way as to support her lies. Sally may, for example, acquire media companies so that she may propagate a global false narrative that would support her lies by giving her audience the impression of consistency and reputability. She may also use financial and political influence to censor independent news sources, falsely link the sources of legitimate criticism to outrageous conspiracy theories so as to introduce doubt about the sources’ credibility, ridicule her critics by capitalising on sensitivities, insecurities and prejudices of her audience, or covertly employ experts and scientists to corroborate her false claims. She may thus ultimately create a web of mutually-validating lies so intricate and pervasive that the truth, the objective truth, would appear as falsity, and anyone promoting it would seem a liar, hater and a villain. The question of epistemic legitimacy in a world of pervasive deception would then come down to “Who decides the conditions of truth?” (Lyotard 1984, 29). The goal of all propaganda is to maintain monopoly over the conditions of truth.

In order to function in the world we must make assumptions about facts and about logical relations between facts, and it is often not possible for us to verify all the relevant information. We are inherently prone to error and therefore susceptible to being deceived, but we can reduce the likelihood of being deceived by consistent application of sound reasoning. The most dangerous epistemic fallacy, in my view, is the idea that consensus of experts entails the most reliable estimation of the truth, but subject-matter expertise has no bearing whatsoever on whether the experts speak truthfully. There is no causal relationship between motivation to deceive and subject-matter expertise. Experts can and do lie when it serves their interests. Furthermore, the notion of ‘consensus’ is itself not epistemically relevant; consensus is a state of discourse, not an epistemic conclusion. It is significant that the epistemic process cannot be brought to a conclusion by preponderance of evidence and positive inference, not even probabilistically, because contingent truths are essentially uncertain. Only non-sense, contradiction, constitutes a definite epistemic boundary, a negation of a premise or the end of logical argument. This account of the epistemic process is reminiscent of Camus’ insight that “one recognizes one’s course by discovering the paths that stray from it” (1975, 103). It may be that we do not immanently ‘recognise’ the ‘true’ course by the paths that stray from it but, rather, we estimate the envelope of possible truths, permissible ideas, based on all the negated epistemic theorems: a logical space delimited by contradictions. Another way, we can narrow the range of epistemic possibilities via progressive identification and elimination of non-sense. Truth, then, is not something that can be given, not a function of trust, it does not come from a reputable source or consensus of experts, but something we must carve out for ourselves, by our own skill and effort. The more consistent we are in our reasoning, the more comprehensive the grounding of our premises, the more difficult we are to deceive, even if sometimes we have to make decisions based on incomplete and uncertain information.

Camus, Albert. The Myth of Sisyphus . Penguin, 1975.

. Penguin, 1975. Carson, Thomas L. Lying and Deception: Theory and Practice . Oxford University Press, 2010.

. Oxford University Press, 2010. Davidson, Donald. Deception and Division , in “Problems of Rationality”. Oxford University Press, 2004.

, in “Problems of Rationality”. Oxford University Press, 2004. Lewis, David. On the Plurality of Worlds . Basil Blackwell, 1986.

. Basil Blackwell, 1986. Lyotard, Jean Francois. The Postmodern Condition: A Report on Knowledge. Manchester University Press, 1984.

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