The concepts "soul", "spirit" and last of all the concept "immortal soul" were invented in order to despise the body, in order to make it sick - "holy" - in order to cultivate an attitude of appalling disrespect for all things in life which deserve to be treated seriously i.
Instruments and playthings are sense and spirit: behind them there is still the Self. The Self seeketh with the eyes of the senses, it hearkeneth also with the ears of the spirit.
The various languages placed side by side show that with words it is never a question of truth, never a question of adequate expression; otherwise, there would not be so many languages. The 'thing in itself' (which is precisely what the pure truth, apart from any of its consequences, would be) is likewise something quite incomprehensible to the creator of language and something not in the least worth striving for.
With regard to philosophical metaphysics, I always see increasing numbers who have attained to the negative goal, but as yet few who climb a few rungs backwards; one ought to look out, perhaps, over the last steps of the ladder, but not try to stand upon them.
We have no organ at all for knowledge, for truth: we know (or believe or imagine) precisely as much as may be useful in the interest of the human herd, the species: and even what is here called usefulness is in the end only a belief, something imagined and perhaps precisely that most fatal piece of stupidity by which we shall one day perish.
To become wise you have to want to experience certain experiences, and so to run into their open jaws. This is very dangerous, tobe sure; many a "wise man" has been eaten up in doing so.