A recent paper by Castro and Granik based on the work of El Naschie has given a rationale for the three dimensionality of our physical space within the framework of Cantorian fractal space-time using similar ideas of quantized fractal space-time and non-commutativity. We also deduce the same result. Interestingly, this is also seen to provide a rationale for an unproven conjecture of Poincaré.