These, I think, are our complex ideas of soul and body, as contradistinguished; and now let us examine which has most obscurity in it, and difficulty to be apprehended.

I know that people whose thoughts are immersed in matter, and have so subjected their minds to their senses that they seldom reflect on anything beyond them, are apt to say, they cannot comprehend a THINKING thing which perhaps is true: but I affirm, when they consider it well, they can no more comprehend an EXTENDED thing.
23.

Cohesion of solid Parts in Body as hard to be conceived as thinking in a Soul.
If any one says he knows not what it is thinks in him, he means he knows not what the substance is of that thinking thing: No more, say I, knows he what the substance is of that solid thing.

Further, if he says he knows not how he thinks, I answer, Neither knows he how he is extended, how the solid parts of body are united or cohere together to make extension.

For though the pressure of the particles of air may account for the cohesion of several parts of matter that are grosser than the particles of air, and have pores less than the corpuscles of air, yet the weight or pressure of the air will not explain, nor can be a cause of the coherence of the particles of air themselves.