What Is The Soul?
"What is the soul" is, of course a question that profound thinkers, theologians, and philosophers have attended to since the beginning of souls. We can see and feel our material form, our bodies, but we know 'we' are inside, we know there is some 'self' that is more than the muscle and tissue composition we move around in - we know our bodies are containers. What exactly it is that they contain is, of course, the question. What are we, how do we come by this notion that we are an invisible being inhabiting a material container?
Certainly a recognition that while the body operates as a tactile apparatus, moving us about and handling items in our material world, etc, there is a thinking component, an administrator, a supervisor or director of the body, can be agreed upon. Now, that thinking component could be simply another feature of the material body, the 'operating procedures' feature of the physical system of the body - except, the thinking component doesn't merely operate the body, it contemplates and dreams, it knows fears and hopes, it enjoys fond memories and is anxious about the future, etc. There is something more inside our bodies than merely a headquarters of bodily operations.
A Christian View
My own understanding of 'the soul', what and why it is, I gain from my Christian faith. "Christian faith" means that I accept God's point and purpose in all that is as good and right, my confidence rests not in my own intellectual capacity to discover and comprehend all things, but in God's willingness to reveal to me what He determines to reveal to me. God has given me a good working mind and He calls on me to use reason, so I'm not suggesting that anything I hear from any source asserting to be 'the word of God' I uncritically adopt as my own view - I'm saying that as I consider things, as I collect evidence and examine ideas, I count God to be the authoritative source of real truth . . . so that, if the whole world says 'A', and I've always thought 'A', and 'A' seems the sound thing to me, if God asserts 'B' then I will count 'A' as the way things apparently seem and 'B' as the way things factual are.
Of course the trick to holding this position, as we consider the nature of 'the soul', is that God doesn't explain to us just what the soul is - in fact, what the Bible does talk about is that while man is a union of body, soul, and spirit, man is unable to even distinguish between the soul and the spirit. But God does provide us with some thoughts to consider. In the Genesis account of creation, God reveals these two specifics regarding His creation of man; first, God tells us that "God created man in His own image". Now, we're confident that this is not suggesting that we look like God, that our material form resembles a material, physical divine being. Instead we understand that our likeness to God refers to the fact that we are not merely conscious but are self-aware, that we have a cognitive not just instinctive thinking process, that we can observe, gather, and process information (we see & hear, etc, the world around us and we draw conclusions about what we observe), and that we own a capacity to make real and consequential choices regarding the world we exist in, etc. This all, again, suggests a 'self' beyond or inside the material body we exist in.
"Man Became A Living Soul"
Next, Genesis gets a bit more specific, telling us "the Lord God formed the man of dust from the ground and breathed into his nostrils the breath of life, and the man became a living soul". For me, this passage sets-up my general understanding of what the soul is. "Formed from the dust" suggests to me the material stuff of our physical body - part of what we are is material existence. The word "breathed" of "breathed into" is the very word often used in Scripture for 'spirit', so I take this phrase to suggest that God's own Spirit is what imparted life into our body - part of what we are is living spirit. The "became a living soul" is, of course, the telling statement . . . it seems to me God is here telling us that, when a material form is brought to life by a living spirit, the union of material & spirit, body & life, the visible & the invisible, that merger, or fusion, creates the unified being we call 'a soul'. Because man is not merely an instinctively functioning body (like a rose or a trout) and is not exclusively a disembodied life-force, but can observe and process information (see & hear, etc) and has consciousness of his existence and owns a capacity of free volition, because of these distinct but united together features, man is not just a functioning body and not just a dynamic spirit - man is a living soul.
Now, for me, this raises a very compelling question; does God have a soul? God identifies Himself as the invisible God, the infinite and eternal spirit not contained in a material body - yet, in the fullness of time, God took upon Himself human form, He was born of a woman, begotten in the flesh. When God stepped out of eternity, into His creation, and became the man Jesus of Nazareth, did the very nature of God change . . ? . . when the Spirit of God united with a material body in the person of Jesus, did God become a living soul? The Bible tells us that one of the defining features that makes God the God that He is, is that He is unchanging - but did God so love the world that He stepped out of His eternality and into time in such a manner that He, in time, altered His own eternal nature?
A Cautionary Conclusion
I know we cannot answer this question and I don't think we should fiddle with the idea too much at all - my point in even raising the question in my own mind and sharing it here with you is that we ponder the wonder of what God did in taking upon Himself human nature to save His people from our own corruption . . . that we contemplate from time to time that great step that God took to rescue us from our rebellion against Him. We can't know exactly what that step was and how great a step it was, we can't know the nature or consequence of that most remarkable step, but we can adore, worship, and thank Him for taking it.