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 do 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 2. 12. 34).
Whence and how do 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
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