Animals are conscious beings. An immaterial process is not required for that. They can process and respond to sensory information and their needs as a unified whole. They can have urges to protect and care for their young and act according to their nature to do so. They can even imagine and conjure up mental images. That’s not an immaterial process.
An example of rational thinking? Well, consider a chiliagon (a polygon with 1,000 sides). You understand what that is, even if you’be never encountered one. You may not be able to make a mental image of one, or at least not be able to make a mental image of one that’s distinct from your mental image of a 1,001 sided figure, but you understand what each of those are. You can grasp that concept in a universal sense. The same way you can grasp triangularity, or what it is to be a dog or a human, beyond simple mental images and abstractions of those images and sensory information related to encounters with them.You keep this type of running understanding of universals going on in your thoughts. We can direct our will according to these thoughts and carry out our own ends based on this rational thinking. It’s a step beyond the experience and capabilities of other animals. Even if you are skeptical that humans are the only ones with this ability, it’s this power of rational thought that, to my understanding, the scholastic argues can’t be explained as being just a product of the brain, which can make relationships between patterns, create mental images, feel emotions, but can’t actually take on the forms of a thing in itself, that is, grasp the universal as such.
(Note: This is different that other arguments I’ve made against materialism, which doesn’t just say the mind is material, but denies things such as formal causes and final causes as being a part of a material being. That is a more extreme position.)
Edit: I hate typing from my phone. Especially since it insisted on removing the option to turn off auto correct for me.