This makes sense of the A-T terminology. Thank you for the further explication.

Easy to answer. This is simply sloppiness on my part. The correct technical term is, as you say, the possible intellect. Sometimes also called the potential intellect. My problem is that I have not used the terms for some time and in English passive sounds related to the other two terms, even though it refers to something different, something organic. Clearly, the vis cogitativa or cogitative sense, belongs to the organic part of man and is not to be confused with the possible intellect.

The possible or potential intellect is a purely spiritual faculty of the soul and, as such, not subject to empirical observation, whereas the organ related to the cogitative power would be. Even so, it is not the immaterial power itself that could be observed, but only the physiology that the power uses. We must remember that immaterial does not necessarily mean spiritual or strictly immaterial. What is merely immaterial is not extended in space, but still depends on matter for its existence and operations, whereas what is spiritual has no intrinsic dependence on matter at all.

Thank you for answering, Dennis. I am wondering whether your remarks about the passive intellect are in line with Aquinas', however. What you say about the passive intellect above seems to me to apply in fact to the "intellectus possibilis" not the "intellectus passivus." My notes are too long to paste into a combox, but consider for example this:

In III DA l. 10 C745 emotions, memories and such are from bodily passions, and so the passive intellect, which is not without these passions, is a corruptible part of the soul, for these passions pertain to sensitive part of soul, though the passive intellect is called intellect and rational insofar as to some degree it participates in reason and obeys it. In IV Sent 40.1.1 ad 3 Aq says the passive intellect is not the possible intellect but is a particular ratio which is called vis cogitativa, having a determinate organ of the body, sc. middle chamber (cellulam) of head, as the Commentator says. SCG II.60.1 Averroes said that the habits of knowledges are in the passive intellect as in their subject. Thus Av said passive intellect is in the child from the beginning and through it the child receives human species before it understands in act. Aq goes on to say this is false, that it’s through the possible intellect that we acquire human species, not through the passive intellect. 60.4 the passive intellect is only of particulars.

The passive intellect clearly in Aquinas is said to operate by means of an organ, the cerebellum or whatever - I'm not up on my brain anatomy! So can brain research yield results about what Aquinas calls the passive intellect but not, as you say above, about what he calls the possible or the active intellect?

My first reaction to your intriguing question was "I haven't a clue."

The only thing that comes to mind is that there is nothing to empirically verify about human intellectual activity, since it is all strictly immaterial. Thus, the action of the active intellect in using the phantasm of the imagination as an instrumental cause with which to form the impressed intelligible species would not be physically detectable, nor would be the impressed intelligible species itself. Nor would the passive intellect going into its act of understanding the nature when it is activated by the impressed intelligible species be detectable for the same reason, namely, it is all purely spiritual in nature.

In fact, even the phantasm itself, since it, too, is immaterial, would not be directly detectable. Still, the physiological changes in the neurons of the brain associated with the formation of the image would be detectable. But, of course, that level of sensory cognition is not particular to human beings, but is shared by all animal life.

The closest thing to direct detection of even a phantasm or image might be what I once saw in a Psychology Today issue. Researchers tied down some poor rat and made it look at the picture of a triangle before it on a screen. They sliced of the top of the poor creatures head, injected radioactive dye, and then took an x-ray of the brain from above.

To my surprise, what appeared on the x-ray was not a tiny "image," but a large dark-lined similitude of the external triangle. Even then, its sides were not straight, but seemed curved inward as if to follow the contours of the brain's external shape. This might be the closest we come to "seeing" an image in a brain. Yet, it is hard to believe that a brightly-lit multi-colored Christmas tree would appear in any way near to its actual appearance to the eye.

So, I guess the answer to your question, as best I can estimate at this moment, would be that scientific measurement could, at best, merely measure conditions and changes in the brain that are associated with, but not identical to, the subjectively experienced image or phantasm upon which the active intellect acts so as to form the spiritual species which puts the passive intellect into the actual act of understanding some nature.

So, the bottom line from my perspective would be that there really isn't much for natural science to observe with respect to intellectual activity, must less to make verifiable predictions from. Hope that helps.

And then you developed the clues to show that the form (soul) remains while the matter( body) changes due to the nature of metabolism; showing the soul (form) is the prime life source to the body (matter). We have all seen this in people who have gained strength again after serious illness, some even bringing back full bodily health. But if the soul animates the body, can I argue that for a body coming back to full health, it was not just the clean, healthy foods that did it, but the soul? Are you leading to the argument that food alone does not sustain the body?

No, the soul is the shape of the body.The shape is an abstract notion, not a concrete notion.Therefore a concrete soul does not exist.We are only the fisical body (and its shape). Therefore, since the soul does not exist, why would we believe the spirit exists?„God is spirit.”

in the first place, science only deals with 'natural' causes

so they published 'just-so' stories about the aliens seeding life on earth. then, why only on this planet has many life forms? even if their hypotheses is true, then who or what is the 'prime mover'? just like a man who wants to have a muscular body and yet he doesn't do exercises (although he got gym equipments and exercise machines), and yet he's still not muscular..why, because he doesn't use them..