Relativity was Einstein's main research program and scientific project.It was an open-ended program that developed throughout Einstein's scientific career, giving rise to special relativity, general relativity and unified field theory. In this paper, we want to uncover the methodological logic of the Einsteinian program, which animated the whole program and its development, and as it was revealed in SR, GR, and unified field theory. We aver that the same methodological logic animated all these theories as Einstein's work progressed. Each of these theories contributed towards constructing Einstein's ambitious program. This paper is not a paper in the history of Relativity, but, rather, it utilizes our knowledge of this history to uncover the methodological logic of the relativity program and its development. This logic is latent in the historical narrative, but is not identical to it. We hope to show that the Einsteinian relativity project is still relevant today as a theoretical scheme, despite its failures and despite quantum mechanics.