1 IntroductionIn 300 BC, Euclid presented 5 axioms that were said to govern the properties of space[coxeter1989introduction]. For centuries Euclid's geometry adequately described physical theories. Although substantivalists and relationalists disagreed about whether space was causal or not, there was agreement that Euclid's geometry fit. However, in 1904, Einstein published his theory of special relativity (hereafter referred to as SR). This could not be described by Euclidean geometry: it required a new way of thinking. The main solution was Minkowski geometry. In this article I will cover both geometries and the extent to which Minkowski geometry is a true geometry. I will then consider Poincaré's conventionalist perspective on the true geometry of the world, employing ideas from Einstein, Sklar, and Reichenbach to challenge Poincaré's view before concluding that this is not the case, since Poincaré suggests that it matters what geometry we use to describe the world.2 Euclidean Geometry and Relativity Although not the only geometry, Euclidean geometry had reigned in physics until the publication of Einstein's SR theory in 1904. It was then that non-Euclidean geometries began to seem necessary for an explanation of these new theories. Before the theory of RS, it was understood that the Newtonian vision of space and time was correct[sklar1992philosophy]. Now Euclidean geometry could no longer explain the phenomena described by Einstein's theory. Minkowski's solution to the SR problem was to formulate a new geometry, which he published in 1907. Minkowski's geometry was probably not a geometry in the same sense as Euclidean or Riemann (spherical) [hartshorne2000geometry] geometry for now had four dimensions instead of three... in the center of the paper ......have Poincaré's argument of convenience.5 Conclusion Poincaré, Einstein and Reichenbach, each for their own reasons, took the view that there is no true geometry . Poincaré in 1902, Einstein in 1921, and Reichenbach in 1927. In fact, Poincaré's arguments for the absence of true geometry were put forward before Einstein's special relativity was published, and thus before the confusion of geometry was introduced by Minkowski. But despite this, his reasoning supported whether or not Minkowski's geometry was considered true geometry: for to him geometry was simply a matter of convenience. The author believes that, despite Reichenbach's reservations about the interpretation of conventionalism, Poincaré's argument is true. It is not necessary to have a posteriori knowledge to formulate a geometry, because we can manipulate the laws to adapt them to a geometry, we simply may not like the result!