Science at the Crossroads was published by Herbert Dingle in 1972 at the end of a gruelling controversy with the English scientific world about the clock paradox in Einstein's special relativity. It is a seminal text, which allows us to understand and evaluate, with Cartesian clarity, the problem of that paradox. The essay contains a great wealth of philosophical and epistemological ideas and has a classic imprint, rich with sharp and clear distinctions, and very elegant in style.