Merleau-Ponty is by far my favorite philosopher. His contributions inhere in the way he transformed phenomenology. Phenomenology is the key development in Western philosophy. Kant in the Copernican Turn established that the only way to know what is objective is through the subjective, and thus established Idealism as the most significant philosophical approach within the Western Tradition based on Kant’s key insights which no one has managed to supersede in all this time. We are still operating in the envelope created by the Kantian Critiques. I recommend the BernsteinTapes.com recordings in order to get straight precisely what this means and the Hegelian ramification. Bernstein says that all of Continental Philosophy is operating within the Hegelian transformation of Kant. He also says that Hegel and all the others read the Third Critique as a meta-critique of Kant by himself. If you place both of these observations together we see that the envelope of Western Philosophy although it is established by Kant and transformed by Hegel and then reacted to by the Pragmatists we never left that envelope, and that is why the Analytical Philosophers still go back to Kant as does Continental Philosophy. There is a reason the line of Frege, Wittgenstein, Moore, Russell etc. goes back through Kant to Descartes. On the continental side the stream goes back though Husserl via Heidegger via Merleau-Ponty & Sartre via Deleuze / Bataille / Lacan / Derrida via Zizek and Badiou.
Merleau-Ponty plays a key role in the interpretation of Heidegger. His Phenomenology of Perception attempts to interpret ready-to-hand and present-at-hand modalities of Being in psychological terms as grasping and pointing. But in the process Merleau-Ponty discovers for himself Hyper Being which is called by Heidegger Being Crossed Out and by Derrida as DifferAnce. But Merleau-Ponty’s greatest work is the Visible and Invisible in which he in turn descibes Hyper Being as the Hyper Dialectic between Heidegger’s Modal Being and Nothingness of Sartre. But he goes on from there to describe Wild Being. And this is the key transformation which Deleuze picks up on and attempts to exploit. Just as Derrida is building a philosophy at the level of Hyper Being, so Deleuze works (Thousand Plateaus, Anti-Oedipus) to build a philosophy at the level of Wild Being. There are other attempts like that of John S. Hans in Play of the World, and Cornelius Castoriadis with his term Magma. So Merleau-Ponty kicked off a gold rush to create a philosophy that could exist at the Wild Being level of the meta-levels of the Kinds of Being. in effect this defined the opposite of DifferAnce of Derrida. To me this is the real value of Merleau-Ponty’s work. Without him I don’t think we would have discovered Wild Being for a long time. He got there by a very simple path. If Hyper Being is the expansion of being-in-the-world then there must be a counter Being which embodies contraction as well.