Fichte and the Dream Argument Dietmar H. Heidemann Introduction There can be no doubt that the dream argument is one of those philoso- phical arguments that at first glance seem to be equally straightforward and simple but turn out to be most complicated and tenacious. The dream argument essentially consists of two interconnected claims: first, dreaming states are not a reliable source of the epistemic justification of beliefs, and, secondly, there is no criterion to distinguish waking states from dreaming states. Whereas the first claim can be regarded as unproblematic, since we in fact do not take dreams to be an acceptable source of epistemic justifi- cation of our beliefs, the second claim turns out to be the real philosophi- cal problem. For if there is no criterion to distinguish waking states from dreaming states, we can never know whether our beliefs are true, because dreaming states do not provide a reliable basis to justify them. Descartes’ Meditations represent the locus classicus of the dream argu- ment. The reason for this is that Descartes does not consider the dream ar- gument to be merely a philosophical idea of somewhat general interest. He rather presents a paradigmatic analysis of the dream argument. The Cartesian analysis is even the reason why the dream argument is still a controversially debated topic in contemporary epistemology and philo- sophy of mind. Also Fichte takes it to be a particular philosophical chal- lenge. To Descartes the dream argument comes in form of the so called skep- tical hypothesis, i.e., an abstract description of a non-excludable skeptical 358 Dietmar H. Heidemann possibility. According to that skeptical possibility, it could be the case that our beliefs appear to be subjectively justified though in fact they are not. By means of the skeptical hypothesis the skeptic attempts to show that we cannot know whether our beliefs are true, for we are not able to rule out the skeptical hypothesis to be true. In general, the argument based on the skeptical hypothesis SH has the following structure: (1) I do not know that not-SH. (2) If I do not know that not-SH, I do not know that p. Conclusion: Therefore, I do not know that p. Thus the skeptical hypothesis argues that we cannot exclude that our epi- stemic situation is controlled by that very skeptical possibility. It does not claim that this in fact is the case. However, if there is knowledge, the skep- tical hypothesis must be wrong, and, moreover, we must know that it is wrong. Furthermore, for the whole argument it is most crucial that the analysis of our beliefs does not inform us about the truth of the skeptical hypothesis.1 The Meditations provide two particular examples or versions of the skeptical hypothesis, the dream and the evil demon hypothesis. In the First Meditation Descartes develops an argument according to which sense per- ception cannot function as a reliable source of knowledge because from time to time our senses deceive us. Alternatively, at first glance physical self-perception seems to be indubitable, and therefore, in the epistemic sense, safe. However, there is the possibility that the conscious perception of our own body turns out to be a dream and that all of our outer percep- tion is nothing but mere hallucination. According to the dream hypothesis, we might well know the difference between dreaming and waking as such; but we do not have at our disposal a criterion that would make it possible to discriminate waking states from dreaming states without any remaining doubt. That is to say by means of no epistemological analysis whatever of a particular belief, we would be able to determine the truth or falsehood of that belief. This also holds true of the evil demon hypothesis in Descartes’ Meditation according to which our beliefs are controlled by an evil demon 1 On the nature of the sceptical hypothesis cf. Williams, 1996, pp. 79–83, and Nozick, 1981, pp. 263–264. See also Heidemann, 2007, p. 3 ff..