First off, I know that I've been absolutely lax in updating posts. I hope to do better in the future, but... we'll see how well I do. That said... on to the post...
There's a common understanding in the metaphysical and spiritual communities that we are all, ultimately, One, and that we are not separate from one another. All of this distinction is an illusion. I don't buy it.
Mystical experiences aside for now, this simply does not match up with what we see in reality. Look at anything and what you see is not a single Oneness. My spleen is not the same as my heart, but they are both part of my body, and anything affecting the heart will affect my spleen, and vice versa. Everything is connected, and part of a greater whole, but that doesn't mean they are one or the same thing.
The same applies in nature. The wolf and the deer are not the same, they are distinct entities, but they are connected in multiple ways, and both part of a greater whole (the forest ecosystem, among other possibilities). The slug and the tomato, the water and the wind, the chair and the desk - all of these are distinct, but part of a greater whole in multiple ways (the garden, the sea, the office).
If we look at these examples as signs of how reality works, then there is no sense is which we are all One. We are all parts of a Whole, but we are not One, in any way. I am not You, and that's a good thing. The diversity of Nature is vitally important to ongoing success. All the various parts in your body, doing different things for different reasons, all at the same time - this is how we are healthy and living. Even similar or identical kinds of entities are not the same - THIS white blood cell is hunting down pathogenic bacteria in the big toe, and THAT white blood cell is currently digesting a different pathogen somewhere in lymph nodes in the neck. They are different and separate, and that's vitally important to the success of the Whole.
Separate does not mean disconnected though. Nor does it mean not important. We are not a Unity, but we are a Wholity, with all our parts having important roles to play in the overall success of "Me" or "You". And as individuals, you and I are also parts of another greater whole, which the same kinds of connections and impacts. Every action I take will influence all of the other parts of my whole in some way, positive or negative. If I go out and do "good", this will affect the way that Men / Humans / <insert your own favorite group/whole here> will be perceived. And the "bad" acts will do exactly the same in the opposite direction. The consequences of my acts affect everyone.
These consequences ripple through the whole not because we are the same, but because we are not the same. The Whole is not a diamond, but a complex mixture more like jello, allowing movement and transformation all throughout. The movement and ripples will affect each of us differently, because we are distinct and our connections are varied.
Next time someone tells you we're all One, go look out the window, and see for yourself if that really holds up.