My advice would be to not begin your investigation with too literal a brush. There are of course western philosophers who are highly educated and world-influencing Buddhists, but let’s leave them out of the discussion since Buddhism isn’t of western-origin.

I think the closest you’ll come is Gaia theory, which postulates that the earth itself is a single living organism. Most scientists, including myself, believe that that it literally true, but not to the degree that it’s sometimes taken by the non-scientific community (typically as written about in softcover books with a green leafy goddess on the cover).

Everything interacts and everything co-evolves. This might include predation, pollination, guarding, harassing, harvesting, and so on. It’s not one big happy family, but you can’t go too far down the “red in tooth and claw” path either. It’s far more complex and interesting in the state of nature than a war of all against all.

Of particular interest are the eusocial (truly social) animals, such as ants. In many ways, it’s incorrect (or at least very incomplete) to think of an ant as an animal in and of itself. The colony itself can be thought of as an animal, with the individual ants being closer to the relationships between cells and bodies.

Some scientists (including myself, but also people like EO Wilson) believe that humans are eusocial. We are beyond a doubt and by far and away the most social of the primates (“You will never see two chimpanzees carrying a log together” is one famous saying. While mammals in general cooperate as well as compete with conspecifics, nothing except weirdly the naked mole rat comes close, and Wilson attributes the human conquest of the earth to our ability to cooperate.

Still, we have conspecific violence ranging from abuse to bar fights to wars. Biology is messy.

Anyway, that’s the closest I can call to mind, and it has the additional benefit of being something that can be experimentally and observationally investigated as well as quantified.

Spinoza?

In his metaphysics, everything that exists is part of a single substance, which he calls Deus sive Natura (God or Nature). This substance is infinite, eternal, and indivisible, encompassing both mind and body as two aspects of the same fundamental reality. As such, the distinction between subject and object, or mind and matter, is ultimately illusory; they are simply different attributes of the same underlying substance.