Isn’t it strange that being our soul an immaterial simple being able to reflect, we need to ask someone else “do we become identical to the thing we know?”? But even more surprising is that the answer has to be an analogy, and the language one that we use to talk about material entities. If it is true that reality produces an impression on our mind, this is… very strange
Whether it is surprising or not, I will leave for you to decide

.
However, it makes sense, when we reflect upon it. Our primary object of knowledge is the things in the world outside. The interior workings of our intellect are a mystery that is only penetrated with difficulty.
We have to use analogy, because our intellection is a spiritual reality. Our minds work directly with material realities. As you have pointed out many times—and I have agreed with you on this—we have to use analogy to understand
anything that is beyond sensory experience.
The clay, which according to the aristotelian philosophy is a composite of prime matter and form, assumes the geometric form of the cube and looses its previous form.
Its geometric figure, yes. Its substantial form, no. The clay remains clay; it does not become wood (which is what would happen if it changed its substantial form).
According to the Thomist philosophy a soul is a form. If the soul knows the geometric form of the cube, and it is true that it becomes identical to the thing it knows, then it acquires the geometric form of the cube. Then it is a form which becomes another form remaining, nevertheless, basically unchanged. This is no analogy.
It is the prerogative of spiritual substances to have an operative faculty—the intellect—that is capable of taking on even the substantial form of other substances. That is their particular similarity with God: that they can conceive (make concepts of) things in their intellects (and also love them with their wills).
But, don’t we know the geometric form of the cube? We certainly do!
I never denied that…
So, our soul must take geometric forms; but if takes geometric forms, then it is not immaterial.
It can take on those geometric forms in an intellectual (intentional) way.
Don’t forget that the intellect works closely with the imagination when it knows geometric figures like this. The abstraction of the “figure” is the whole basis for geometry. (Notice that squares and circles do not exist in reality in exactly the same way that geometry textbooks define them. The objects of Euclidean geometry are abstract idealizations of reality.)
But it is immaterial, therefore it does not take geometric forms. But we know geometric forms, therefore, to know something is not to become identical to it.
God is spiritual. Does it imply that He is “malleable”?
He is not malleable, but He does not need to be, because He already knows all of His creatures in His very Essence. We have to pass from not-knowing to knowing, which is why our intellects are changeable. God already knows.
Sub-human creatures are non-malleable by defect. God is non-malleable by excess.
But we should notice as well that the clay losses its previous geometric form. So, strictly speaking it is not the same clay.
Sure it’s the same clay. Why would it be a different clay just because I moved it a little?
We have the same “secondary matter”, which we call “clay” too, but the term was not used in the same sense. So, when the clay assumes different shapes, the “secondary matter” remains unchanged. But if our soul is simple, assuming another form without changing would mean that part of it does not change, while another changes, which is absurd. There is no analogy.
The soul does not have physical parts (which is what makes it simple), but it does have accidents: namely, the intellect and the will (as well as various relations). Hence, we can talk about the soul as if it were a kind of secondary matter—where “matter” here is not physical matter, but simply means a receptive principle that is ready to receive other forms (namely, the intellect and the will).
Spiritual creatures are so noble, in comparison to sub-human creatures, that, not only can their
soul receive forms (like the intellect and the will), but even one of its operative capacities (the intellect) can receive forms.
If we pay attention, we see nothing clear really.
If there is a group of persons around an object, would all of them be impressed by it in the same way?
In the same way in general, yes. We all apprehend enough about an object to be able to speak to each other about it and know what we are talking about.
In the same way in every specific detail, no. I think this is obvious. (I have stated many times that we know things from the outside in: from the more general to the more specific. People differ in their penetration of the mystery of an object; they may also follow different paths to more specific knowledge.)
If that were true, we wouldn’t need to speak.
But we also would be unable to speak about such an object unless we had a common understanding of it.
If you want to convey a message to someone, just point with you finger towards the object of your intellection: he should be impressed by it in the same way. But obviously, it does not happen.
There is something really wrong in the belief that reality impresses itself on our minds…
On the contrary, it is necessary for there to be communication at all. Otherwise, no one would understand what the other was speaking about. Also, even assuming we had perfect, comprehensive knowledge of an object (which we do not), language would serve to learn about things we
cannot see directly.