I would be happy to open a line of discussion about this topic.
OK. Lets look at the immateriality of the intellect.
First, the basic Aristotelian principle is that nothing is in the intellect that was not first apprehended by the senses. The senses create sense images or phantasms in the mind that represent the singular instance of the object observed. These images get stored in memory.
Along with the animals, bodily organism feels attracted or repelled (or potentially indifferent) by sense objects. It also has what Aquinas called the irascible response where animals either overcome difficulties by confrontation (fight response) or by avoidance (flight response).
So, as you can see, there is a way in which animals are conscious, but their reactions are instinctive and biologically driven.
Human beings have the added level of the intellect. What happens here is that the human intellect abstracts (dematerializes and de-individualizes) the sensual images, removing differences of size, color, and location. For example, the intellect takes the image of a particular triangle, and abstracts from all individualizing specifics to focus on the essence of triangularity.
The intellect grasps essences. And based on this world of essences that it absorbs from the sensual world from an early age, the intellect builds up a structure of further concepts and ideas, such as being, truth, beauty, and the like. This is mankind’s intellectual world in a nutshell. It is immaterial and universal. Human beings can also focus the intellect on the particular as well, but it does so based on this framework of immaterial universals.
As you may be aware, modern science has a heck of a time explaining things like qualia, intentionality, and intellect. Eliminative materialists deny that qualia, intentionality, and intellect exists at all. Emergent materialists say they do exist, but they somehow emerge from material processes. Scholastics believe that there is no way in principle that intellect can develop from material processes on account of the immaterial nature of the things contemplated in the intellect. Although the intellect depends on the senses to gather abstractions and create concepts, and granted that the corruption of aging has a serious impact on the intellectual faculties, the intellect remains due to its immateriality. It must be immaterial on account of the immaterial things it contemplates. It must also have its source directly in God if material processes cannot account for its existence.
I believe that the Scholastics are right. I also believe that this is also a good starting point to understand what a simple immaterial angel or the simplicity of God would be like.
God bless,
Ut