Answer
Martin Heidegger's existentialism shares similarities with Ortega y Gasset's earlier proto-existentialism. Both philosophies emphasize the importance of individual existence, the significance of personal choice, and the role of circumstance in shaping human experience. However, Heidegger's existentialism is more abstract and metaphysical, focusing on the existential structure of being, while Ortega y Gasset's proto-existentialism is more concrete and pragmatic, emphasizing the lived experiences and perspectives of individuals.