Avicenna believes intellectual progress is made through finding the linking, or middle terms, of syllogistic arguments. A thought experiment is not in itself a syllogism, but it can prompt one to reflect more effectively and help trigger and intuitive insight of that elusive middle term. More modestly, a thought might just guide one towards the right conclusions for which one could then seek a good, demonstrative proof. So, Avicenna was a devoted user of thought experiments and other ways of prompting himself and his readers to reach new insights. Avicenna’s most famous thought experiment is the floating man thought experiment. Avicenna’s floating man thought experiment is supposed to explain his idea of self-awareness. The floating man will, according to Avicenna, have knowledge of his or her own essence or self. The floating man is sometimes compared to Descartes’ cogito ergo sum, because the thought experiment appeals to the inevitability of grasping one’s own existence, but Avicenna is not trying to radical skepticism, which was the purpose of Descartes’ cogito. Rather, the floating man has a different purpose. Most obviously, the floating man draws attention to the phenomenon of self-awareness. Avicenna was fascinated by the fact that humans are all always able to become aware of their own existence.
The difference between the floating man and normal human beings is that normal human beings souls are full of the deliverances of sensation, memory, and thoughts. This might fool one into supposing that when he or she is self-aware, he or she is aware of only that he or she is having some sort of sensory experience, some memory, some thought, but Avicenna insists that self-awareness is more fundamental than any such mental activity. Indeed, all other mental activity presupposes self-awareness, since whatever one thinks or experiences, this individual must always be recognizing it as his or her own thought or experience. Of course, humans are not always actively aware of this self-awareness; rather, individual’s primitive self-awareness is a kind of background foundation for all mental life. Avicenna claims that this goes on even during sleep. To become actively conscious of this self-awareness, individuals need to focus on the self-awareness deliberately, and the floating man thought experiment is one-way Avicenna help to do that.
This type of self-awareness is supposed to explain that minds are immaterial and perfect (unitary). This is because, in the Aristotelian tradition, knowledge in the strict and proper sense should be directed at universals. So, if an individual was to know about lions, then he or she is grasping the universal lion, rather than any individual lion. Furthermore, material substance is what makes lions distinct from one another. Since lion A consist of one batch of matter arranged as a lion, while another lion, lion B, consists of another batch of matter, then lion A and B are distinct. That suggests that if our minds take on a universal, rather than particular form, then our minds must be immaterial and therefore, perfect (unitary).
Avicenna thinks this type of self-awareness is philosophically important because he considers only the intellectual part of the soul, what he calls the rational soul, to be separate from body and its activity. In fact, just like lions, the human soul needs matter in order to be the specific soul that it is. What makes two souls distinct is that they are two separate forms, given by the active intellect (which is always actualized), to two different bunches of matter. Whenever a bunch of matter is prepared in the correct way an appropriate form will emanate from it. Before this emanation into some particular matter, the soul does not exist.
This causes Avicenna some problems at the other end of the life cycle. Since the only aspect of the soul that operates without bodily organs is the intellect, it is only the intellect that will survive the death of the body. However, this leads to another problem. Once there is no body to be connected to, how will the immaterial soul be distinguished from any other soul? Perhaps the difference is that each soul has a unique range of universal thoughts. Person A has spent his or her life researching lions, while person B has spent his or her life researching zebras – this is what will differentiate the two after death. Here, it is worth noting that in an indirect way, the soul actually needs the body in order to continue its activities after death. After all, how could person A know about lions or person B knows about zebras if neither had ever been in a body? With the exception of a few basic first principles and concepts, Avicenna thinks that knowledge is derived from sense-experience. Avicenna thinks an individual absolutely need the body if he or she is to activate his or her intellects and live the life of the mind, whether during embodied existence or thereafter.