 A posteriori necessity

A posteriori necessity refers to a philosophical concept concerning the nature of necessary truths that can only be known through experience or empirical evidence, rather than through pure reason or a priori reasoning. To break it down: - **A posteriori** knowledge is knowledge that is gained through experience or observation. For example, scientific knowledge, derived from experiments and empirical data, is a priori. - **Necessary truths** are propositions that could not have been otherwise; they hold in all possible worlds.