Medieval philosophy a new history of western philosophy volume 2 ( PDFDrive ) 176

KNOWLEDGE I know that I am alive, I know that I know that I am alive, and so on ad inWnitum Sceptics may babble against the things that the mind perceives through the senses, but not against those that it perceives independently ‘I know that I am alive’ is an instance of the second kind (DT 15 12 21) Those who have read Descartes cannot help being reminded here of the Second Meditation; and indeed arguments akin to ‘I think, therefore I am’ are found in several of Augustine’s works In The City of God, for instance, in response to the Academic query ‘May you not be in error?’, Augustine replies, ‘If I am in error, I exist.’ What does not exist cannot be in error; therefore if I am in error, I exist (DCD IX 26) Each of us knows not only our own existence, but other facts too about ourselves ‘I want to be happy’ is also something I know, and so is ‘I not want to be in error’ But the mature Augustine accepts the truth of many propositions besides the Cartesian certainties We should not doubt the truth of what we have perceived through sense; it is through them that we have learnt about the heavens and the earth and their contents A vast amount of our information is derived from the testimony of others—the existence of the ocean, for instance, and of distant lands; the lives of the heroes of history and even our own birthplace and parentage (DUC 12 26) Throughout his life Augustine gave a place of honour to the truths of mathematics, which he classes as ‘inward rules of truth’: no one says that seven and three ought to be ten, we just know that they are ten (DLA 12 34) Whence and how we acquire our knowledge of mathematics, and our knowledge of the true nature of the creatures that surround us? In the Confessions Augustine emphasizes that knowledge of the essences of things cannot come from the senses My eyes say ‘if they are coloured, we told you of them’ My ears say ‘if they made a noise, we passed it on’ My nose says ‘if they had a smell, they came my way’ My mouth says ‘if they have no taste, don’t ask me’ Touch says ‘if it is not bodily, I had no contact with it, and so I had nothing to say’ The same holds of the numbers of arithmetic: they have no colour or odour, give out no sound, and cannot be tasted or touched The geometer’s line is quite diVerent from a line in an architect’s blueprint, even if that is drawn thinner than the threads of a spider’s web Yet I have in my mind ideas of pure numbers and geometrical lines Where have they come from? (Conf X 11 17–19) Plato, in his Meno, had sought to show that our knowledge of geometry must date from a life before conception: what looks like learning 157