The great philosopher Ludwig Wittgenstein once wrote, "Philosophy leaves everything as it is'. That is, philosophy does not change anything, and can never change anything. We may think — I indeed think — that that was a foolish remark; doubtless all philosophers, even great ones, make foolish remarks sometimes. There are many people who would vehemently repudiate Wittgenstein's observation — followers of Karl Marx, for example. We know, and have been celebrating, how greatly Brouwer's philosophy changed mathematics — not, alas, for all mathematicians, but for a select band, so well represented here, able to understand and appreciate Brouwer's insights.