Identity of Indiscernibles
[WORK IN PROGRESS]
Famous slogan of Leibnitz. My off-the-cuff idea of what Leibnitz intended with this doctrine is that if two things share all the same properties then they must necessarily be the same thing! This is clearly contrary of Ross’s ontology, because remember, for Ross, nature is what makes something act or behave the way it does. Thus he distinguishes between the “components” of a natural thing that make it behave the way it does and the “overflow necessities” of the thing that are necessary for its existence but which do not determine its behavior.
The Identity of Indiscernibles doctrine is also related to Leibnitz’s idea that nothing has a purely external denomination (See definitions of internal & external denomination below).
Here’s a commentary about the Identity of Indiscernibles that I found on the internet:
A principle of analytic ontology first formulated by Leibniz which states that no two distinct things exactly resemble each other. This is often referred to as ‘Leibniz’s Law’ and is typically understood to mean that no two objects have exactly the same properties.
It is of interest because it raises questions about the factors which individuate qualitatively identical objects. Recent work on the interpretation of quantum mechanics suggests that the applicability of the principle in the quantum domain is controversial.
Most formulations of the Principle carry a prima facie commitment to an ontology of properties, but nominalists of various kinds should have little difficulty in providing suitable paraphrases to avoid this commitment.