Surprisingly, the fact that the speaker is lying is sometimes common knowledge between everyone involved (the addressee, the general audience, bystanders, etc.). Strangely, we condemn these bald-faced lies more severely than disguised lies. The wrongness of lying springs from the intent to deceive -just the feature missing in the case of bald-faced lies. These puzzling lies arise systematically when assertions are forced. Intellectual duress helps to explain another type of non-deceptive false assertion: lying to yourself. In the end, I conclude that the apparent intensity of our disapproval of non-deceptive lies is a rhetorical illusion.

If a spinning disk casts a round shadow does the shadow also spin? When the cave guide turns out the light so that you can experience the total blackness, are you seeing in the dark? Or are you merely failing to see anything (just like your blind companion)? Seeing Dark Things uses visual riddles to explore our ability to see shadows, silhouettes, black ants, plus some things that are only metaphorically “dark” such as holes. These dark things are anomalies for the causal theory of perception: anything we see must be a cause of what we see. Roy Sorensen defends the causal theory of perception by treating absences as causes. With the help of fifty-nine figures, Sorensen proceeds bottom up from observation rather than top down from theory. Shadows are metaphysical amphibians with one foot on terra firma of common sense and the other in the murky waters of nonbeing. Seeing Dark Things portrays the causal theory of perception's confrontation with the shadows as a triumph against alien attack. Lessons from the parried threat deepen a theory that resonates strongly with common sense and science. Thus the book is an unorthodox defense of an orthodox theory.

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This is a defense and extension of Stephen Yablo's claim that self-reference is completely inessential to the liar paradox. An infinite sequence of sentences of the form "None of these subsequent sentences are true" generates the same instability in assigning truth values. I argue Yablo's technique of substituting infinity for self-reference applies to all so-called "self-referential" paradoxes. A representative sample is provided which includes counterparts of the preface paradox, Pseudo-Scotus's validity paradox, the Knower, and other enigmas of the genre. I rebut objections that Yablo's paradox is not a genuine liar by constructing a sequence of liars that blend into Yablo's paradox. I rebut objections that Yablo's liar has hidden self-reference with a distinction between attributive and referential self-reference and appeals to Gregory Chaitin's algorithmic information theory. The paper concludes with comments on the mystique of self-reference. An infinite queue of students receives a lecture on human fallibility. Each student thinks (Q) Some of the students behind me are now thinking an untruth. As it happens, each student is thinking just one thought: (Q). Of course, their different positions in the queue ensures that each token of (Q) expresses something different. None the less each of their thoughts is paradoxical. Consider student n and his thought (Qn). If (Qn) is untrue, then all of the students to his rear are thinking truths. But their thoughts can only be true if some of their successors are thinking untruths. Contradiction. If (Qn) is true, then some subsequent student is mistakenly thinking "Some of the students behind me are now thinking an untruth". But it has already been shown that a (Q) thought cannot be untrue.

Imagination is associated with escapism, free association, and unfettered thought. Yet thought experiments intertwine with all sorts of reasoning and even in the appraisal of argument. Typically, the validity of an argument is first tested by trying to imagine a situation in which the premises are true and the conclusion false. For example, George Simmel invalidated Nietzsche's argument for the eternal return by envisaging a universe containing three wheels on a single axle spinning endlessly at rates n, 2n, and pi/no (The incommensurability introduced by the irrational number pi ensures that the wheels never re-align.) Enthymemes are reconstructed with a curious crew of fictions: the devil's advocate, the reasonable man, the ideal thinker, etc. Definitions are refuted by (often highly) hypothetical counterexamples: Russell's five minute hypothesis, the Ship of Theseus, Aquinas' cannibals. Imagination also figures prominently in less understood acts of clarification such as idealization.True, logicians often try to break free of any reliance on imagination. The formal strategy is to disinterpret an argument into inert symbols and let the proof proceed by purely syntactic means. But this two dimensional symbol manipulation only applies to arguments that have been translated into the calculus. Thought experiment is well-represented at this interface between informal and formal logic because the translator must test the faithfulness of the translation by trying to imagine whether the statement could be true while its translation is false. Crucial logical points have themselves been made by thought experiment. Recall Lewis Carroll's debate between Achilles and the Tortoise, Quine's radical translator, and Wittgenstein's woodcutters. Hypotheticals have enriched our logical vocabulary with 'grue', 'tonk', and 'quus'.Nevertheless, methodical sorts who demand clear reasoning from clear sources of evidence are apt to be suspicious. Thought experiments seem to give you something for nothing. The thought experimenter starts out ignorant. Then he sits in his armchair. Instead of looking, smelling, listening, and so forth, he blocks out empirical data and uses his imagination. He then rises with the answer. What, short of parapsychology, could account for this cognitive transformation?The skeptic challenges the presupposition that the thought experiment proves something. He grants that the thought experiment might be relevant to the context of discovery (like a dream) but not the context of justification. My main response in Thought Experiments is to present a variety of scientific thought experiments that are acknowledged as proof by scientists. I then rely on meta-

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