The philosopher can reflect on the ordinary man's awareness of attaining truth, but he has not at his disposal some extraordinary and special means of proving that we can know truth or that 'knowledge' is knowledge. If a philosopher were to comment that in this case we can never prove that we can attain proof and that if we cannot prove it we can never know it, Aquinas might reply that the sort of proof which the philosopher is looking for is inherently useless and indeed impossible, but that it does not follow that we cannot both attain truth and also know that we can attain it. We do not need any further guarantee of our ability to attain truth than our awareness or recognition of the fact that we do in fact attain it.