If one were to draw up a compendium of everything concerning spirits which is recited by schoolboys, related by the common people and demonstrated by philosophers, it would, it seems, constitute no small part of our knowledge. Notwithstanding, I would venture the following opinion. If it were to occur to someone to linger for a while over the question: What exactly is this thing which, under the name of spirit, people claim to understand so well, all the know-alls would be put in a very embarrassing position. The methodical gossip of the universities is frequently nothing but an agreement to exploit the instability of the meaning of words with a view to evading questions which are difficult to answer. And the reason for this evasiveness is the fact that the easy and generally reasonable answer ‘I do not know’ is frowned upon in the academies. Certain modern philosophers, as they like to be called, have no difficulty in disposing of this question. Their answer runs: A spirit is a being endowed with reason. No miraculous powers are needed, therefore, to see spirits; for, whoever sees human beings sees beings endowed with reason. But, the argument continues, this being, which in man is endowed with reason, is only a part of man, and this part of man, the part which animates him, is a spirit. Very well, then, before you go on to prove that only a spirit-being can be endowed with reason, please make sure that I have first of all understood what sort of concept I am to form for myself of a spirit-being. The self-deception in this case, though plain enough to be seen with half-opened eyes, nonetheless has an origin which can easily be understood. For that about which one knows a great deal early on in life as a child – of that, one can be sure, one will certainly know nothing later on in life when one has reached maturity. And the man of thoroughness will in the end at best be the sophist of his youthful delusions.

I do not, therefore, know whether spirits exist or not. And, what is more, I do not even know what the word ‘spirit’ means.