I think having mentality is part of what it means to be human, just like having the particular body that characterizes the human species. But people can lose mentality, or most of it anyway (and much of the body too), and they still exist and can still enjoy life. The shape
mentality gets in, such as being greedy, doesn't have anything to do with the fundamental nature of mentality. It is, in my opinion, the result of ignorance and therefore underdevelopment.
But what I meant by our nature goes deeper than the body, emotions or mentality. This is an issue that's been hotly debated here, with materialists insisting we, as consciousness, emerge from material processes, and others of us suggesting that the body may be emergent technology alright, but the consciousness emerging through it is NOT emanating from that biological matter.
Whomever is correct, there still remains the question of what is the nature of consciousness. I defined "nature" above in the water example as that which "must function a certain way because that is how it is." One test for "how it is" is to see what we can and cannot eliminate and still have a thriving consciousness.
Of all that consciousness is capable of, there are only two aspects I think we cannot do without. One defines its fundamental way of functioning, and that is consciousness is aware that it is aware. A Geiger counter is aware in a fashion, but it doesn't know
it is aware. So self knowing is absolutely essential to the nature of consciousness.
The other trait I'll cite usually triggers debate, especially in a science forum where so many want to define our "nature" in terms of evolution, chemistry, and neurons. But I think the second most foundational aspect of consciousness is sensitivity. We are 100% dependent on that to feel ourselves and our environment.
When I use the word "feel" I do not mean the emotions, I mean the ability to experience things. If you think about it even the senses are set up to "feel" light, sound, etc., and then the signals are carried to the brain where we wait to experience them.
Because of our deeply rooted sensitivity we, and all animal life, chase after "feeling good" over and above all other pursuits. There isn't one thing people do which isn't an attempt to feel good or better (even suicide -- and yes, there are many things we do that are unpleasant, but we do them because if we didn't the consequences would be more unpleasant). Of course, what people believe
will make them feel good is another story, and very much what philosophy is about.
Does having one's intellect educated and logical satisfy the need to feel good? Does money, drugs, sex, family, music, exercise . . . ? Well, most people say you need some or all of that, but others say the ultimate in feeling good is to learn how to have it without the need for any externals (excepting life support stuff of course).
They say our dependence on externals for happiness, which are always in a state of flux, leaves us at the mercy of ever-changing conditions. When things are good, we feel good. When things aren't going so good, we feel bad. So, the theory goes, the best way is to learn how to feel good alone, from within, and in that way free your good feeling at least from the ups and downs that are part of living.
Because I believe my nature is to know and feel, that has determined my personal philosophy, which is to learn that which best enhances my knowing and my happiness.