Abstract: Leibniz's Law (or as it sometimes called, 'the Indiscerniblity of Identicals') is a widely accepted principle governing the notion of numerical identity. The principle states that if a is identical to b, then any property had by a is also had by b. Leibniz's Law may seem like a trivial principle, but its apparent consequences are far from trivial. The law has been utilised in a wide range of arguments in metaphysics, many leading to substantive and controversial conclusions. This article discusses the applications of Leibniz's Law to arguments in metaphysics. It begins by presenting a variety of central arguments in metaphysics which appeal to the law. The article then proceeds to discuss a range of strategies that can be drawn upon in resisting an argument by Leibniz's Law. These strategies divide into three categories: (i) denying Leibniz's Law; (ii) denying that the argument in question involves a genuine application of the law; and (iii) denying that the argument's premises are true. Strategies falling under each of these three categories are discussed in turn.
Magidor, Ofra. Arguments by Leibniz’s Law in Metaphysics
2011, Philosophy Compass 6 (3):180-195
Added by: Berta Grimau
Comment: Ideal as a main reading in a course in general metaphysics with a section on Leibniz's Law, at both undergrad and postgrad level.