196. In ancient times those were called "serpents" who had more confidence in sensuous things than in revealed ones. But it is still worse at the present day, for now there are persons who not only disbelieve everything they cannot see and feel, but who also confirm themselves in such incredulity by knowledges [scientifica] unknown to the ancients, and thus occasion in themselves a far greater degree of blindness. In order that it may be known how those blind themselves, so as afterwards to see and hear nothing, who form their conclusions concerning heavenly matters from the things of sense, of memory-knowledge, and of philosophy, and who are not only "deaf serpents" but also the "flying serpents" frequently spoken of in the Word, which are much more pernicious, we will take as an example what they believe about the spirit.  The sensuous man, or he who only believes on the evidence of his senses, denies the existence of the spirit because he cannot see it, saying, "It is nothing because I do not feel it: that which I see and touch I know exists." The man of memory-knowledge [scientificus], or he who forms his conclusions from memory-knowledges [scientiae], says, What is the spirit, except perhaps vapor or heat, or some other entity of his science, that presently vanishes into thin air? Have not the animals also a body, senses, and something analogous to reason? and yet it is asserted that these will die, while the spirit of man will live. Thus they deny the existence of the spirit.
 Philosophers also, who would be more acute than the rest of mankind, speak of the spirit in terms which they themselves do not understand, for they dispute about them, contending that not a single expression is applicable to the spirit which derives anything from what is material, organic, or extended; thus they so abstract it from their ideas that it vanishes from them, and becomes nothing. The more sane however assert that the spirit is thought; but in their reasonings about thought, in consequence of separating from it all substantiality, they at last conclude that it must vanish away when the body expires. Thus all who reason from the things of sense, of memory-knowledge, and of philosophy, deny the existence of the spirit, and therefore believe nothing of what is said about the spirit and spiritual things. Not so the simple in heart: if these are questioned about the existence of spirit, they say they know it exists, because the Lord has said that they will live after death; thus instead of extinguishing their rational, they vivify it by the Word of the Lord.