I think of it as purely a distinction of internal relationship, but in such a way that can only be approached, but never attained, by human intellect.
My personal, and highly imperfect, illustration is that of the brain, perception, and cognition combining to make the human mind. There is the brain, which is fundamentally necessary for the other two processes. Without the crude matter of the brain, the others are impossible. The perception is the senses, which come from the brain but are not material; they are of the brain, but they are not the brain. Cognition is the process by which the perception becomes coherent thought; the senses that are created by the brain become ordered into thoughts, words, images, ect. This cognition is intimately tied to perception and the brain, but it is unique in that it is a rearranging of information, a process that includes will and personal development.
Now each of these processes is fundamental to the human mind. The brain is the root of all mental processes, but without cognition it is merely a lump of fat, and without awareness it is blind even to itself and can not even form cognition. At the same time, however, the human mind IS the brain, because all mental processes can be traced to material reactions and movements within the brain. The human mind is also absolutely perception, however, because without at least being able to perceive the self, the brain can not function in a human way, and becomes random firings of electrical pulses and chemicals with no development from them. Our senses define who we are, our place in the world, and are the fundamental building blocks of our personalities;our senses are to our cognition what our material cells are to our perception. Cognition is the capstone, and it is also absolutely the human mind, because without cognition the brain and the perception are nothing but a lump of fat that records impulses like a microphone and hard drive, or a paper and pen. A human mind is because it can order its perceptions in its own way, it can will that data into forms that are unique, and can send that data back out into the world, or at least reflect upon it further to build new forms.
The interactions between these three things can be fuzzy, and the exact nature of each seems to encompass the others when taken individually (for example the crude matter can be taken to be all that there is to the brain, with cognition and senses being illusions, or visa versa). They are known purely by there relationship to one another: the senses perceive the fatty tissue which we call a brain, and our cognition recognizes it as the source of our senses, and the brain processes all of this information continuously. We perceive because of our brain, we know it’s a brain because of cognition, and we have cognition because of our perception. We can infer the existance of one because of the relationship between the two others, yet even our own human mind is a mystery to us, and the farthest reaches of understanding forever removed from us. After all, if we were to solve all of the mysteries of the crude matter of the brain, we would still be limited by our perception of the brain, and left with the possibility that the brain was merely an invention of our cognition as we float as bodiless entities communicating telepathically in a void.
Far from perfect, I know, but I think it serves to illustrate how each Person of the Trinity can be fully God, yet have their own unique qualities by virtue of their relationships to eachother.
