Jesus guys stop running around in circles. Argument for identity, or equality, or whatever you wanna call it: We understand the world through propositional knowledge. Propositional knowledge is always accompanied by the fact that it can be quantified. Quantification requires us to stipulate that the relevant properties, (or those particular properties in question), are identical so that we can fit them into a formal notation. Therefore, an identity theory is established based on that stipulation. Resting on that theory, science and mathematics make progress, and we can construct an ontology. Argument against identity, or equality or whatever you wanna call it: The statement x=x is a quantification of identity. No two objects can occupy the same place in space and time. Because of that, no two objects in the physical world can ever have 100% identity of properties. Therefore, x=x, or identity, is a metaphysical construct, or an ideal, and does not ever actually occur in the physical world. The end. Another philosophy minute, brought to you by MrGoodSmoke. Next week's possible subject: "constructing ontologies: is there an irreducible, fundamental property of all objects both physical and metaphysical?" Are you guys gonna keep ignoring me? I thought we were gonna do some philosophy!!! Oh yeah about about that question on human essence..... Sartre said that existence precedes essence. Existence is the same. Essence is not. (is his view). Some people argue against essentialism altogether, as according to Kant, the thing in itself is unknowable.