The vertical axis of objective truth is thus overturned by Nietzsche in favour of the horizontal axis of values. Deleuze is greatly attracted to this. Horizontality in thought, inaugurated in the modern era by Nietzsche, opens the way to thought as creative, as a form of poetry, perhaps. And indeed, Nietzsche is not only a great stylist, but makes an excess of style a part of his philosophy. Deleuze notes that the great philosophers have always been great stylists.
Style confirms the incomparable nature of the philosopher of difference.
Subject', 'actor', and 'cause' are metaphysical notions characteristic of the vertical axis. The latter axis embodies what is entrenched and relatively unchanging, whereas the horizontal axis is always in movement. Deleuze makes substantial use of the principle of horizontality in his readings of Spinoza , Proust, Leibniz , and Lewis Carroll. Thus for Spinoza 'expression' is not an appearance through which an essence is expressed. Nor is morality a set of ideals to which one might aspire.