There is general agreement among scholars of Rnying ma and Bka’ brgyud traditions that the doctrine known as the inseparability of the two truths (bden gnyis dbyer med) marks the culmination of all Buddhist approaches to truth. As a view grounded in Madhyamaka thought but associated primarily with Buddhist tantric views and practices, it is said to transcend the various bivalent conceptions of truth—predicated on attributions of truth and falsity to allegedly discrete types of perceptions and propositions—that were advanced by the main schools of Indian Buddhist philosophy. In this regard, it is framed as the final cure for metaphysical realism (vastuvāda), the view that the objects, properties, and relations the world contains exist independently of how and whether we perceive, experience, or think about them. This talk first explores the genesis and development of this viewpoint, with a special focus on its explication in the Black Snake Digest (Sbrul nag gyi stong thun) by the 11th century Rnying ma master Rong zom Chos kyi bzang po and a little-known overview of this text by the Eighth Karma pa Mi bskyod rdo rje (1507-1554). The talk then proceeds with an examination of the Eighth Karma pa’s distinctive Mahāmudrā interpretation of this fundamental Buddhist tantric doctrine in his Madhyamakāvatāra commentary and related works. It concludes with a consideration of some of its more intriguing philosophical implications.