  Henri Poincare's work on mathematical features of the Lorentz transformations
was an important precursor to the development of special relativity. In this
paper I compare the approaches taken by Poincare and Einstein, aiming to come
to an understanding of the philosophical ideas underlying their methods. In
section (1) I assess Poincare's contribution, concluding that although he
inspired much of the mathematical formalism of special relativity, he cannot be
credited with an overall conceptual grasp of the theory. In section (2) I
investigate the origins of the two approaches, tracing differences to a
disagreement about the appropriate direction for explanation in physics; I also
discuss implications for modern controversies regarding explanation in the
philosophy of special relativity. Finally, in section (3) I consider the links
between Poincare's philosophy and his science, arguing that apparent
inconsistencies in his attitude to special relativity can be traced back to his
acceptance of a `convenience thesis' regarding conventions.
