All is one.
I find this assertion to be clear and unassailable. Something exists, and while that something appears to be manifold (i.e., that's how we experience it), it is nonetheless one. No part can be separated from the whole. Therefore everything is one. By "everything" and "all" I mean the world, the universe, reality. Spinoza calls this alternately substance, nature, and god.
One (reality) is also complete (whole), perfect, and infinite.
It is complete because it is everything. It is perfect because it is complete. It is infinite because it comprises all possibilities, past, present, and future—because there can be nothing more, but it has no limit. (For if it had a limit, there would be something else as well, but it is everything and therefore there is nothing else.)
Everything exists. That is, everything possible has happened, is happening, and will happen. In other words, time is an illusion.
Those are the first-ish principles.