23. The properties of the perispiritual fluid can give us only an idea of it. It is not intelligent of itself since it is matter; but it is the vehicle of the thought, the sensations, and perceptions of the spirit.
The perispiritual fluid is not the thought of the spirit, but the agent and intermediate of this thought. It is in a manner, impregnated by the life of him who transmits it; and, in the impossibility of isolating it where we are; he seems to be one with the fluid, as sound and air seem to be one and the same in such a way that we can, as it were, materialize it. We say, for instance, the air is sonorous; we, in taking the effect for the cause, say that the fluid becomes intelligent.