In the development of a human being to intellectual maturity it is often difficult to pinpoint the crucial changes of phase: those, for example, when a child first recognizes significance in a spoken jumble of sound, or first perceives the logical compulsion of a train of argument. Of such a kind is the glimmering recognition of the structured orderings of conventional symbols which we loosely call mathematics. Not least that we may know ourselves better we find it tempting to analyze this intellectual growth in the giants of the past in all fields of human endeavour, artistic and scientific—where we can, that is, for all too often through lack of historical fact we can know almost nothing of the growth to manhood of a Shakespeare or an Archimedes. A recently renewed interest in the documentary basis which supports the conventional picture of the life and thought of Isaac Newton has led to a vigorous and variegated study of the wealth of existing manuscript material, still too little known, which both cleans and illuminates it and sometimes demands that we repaint it wholly afresh (1). I myself for many years past have been absorbed in the minute study of Newton’s unpublished mathematical papers and find myself drawn back again and again to the question: Where and when did Newton’s mathematical inspiration begin? Let me present a personal viewpoint on the matter which while urging new facts re-interprets the old.