Look at the trees which are tallest if you consider their height, and the broadest if you look at their thickness and the spread of their branches; compared with all this, how small a part of them is contained in the slender fibres of the root? Yet take away their roots, and no more groves will arise, nor great mountains be clothed with trees. Temples and cities are supported by their foundations; yet what is built as the foundation of the entire building lies out of sight. So it is in other matters; the subsequent greatness of a thing ever eclipses its origin. I could never have obtained anything without having previously received the boon of existence from my parents; yet it does not follow from this that whatever I obtain is less than that without which I could not obtain it. If my nurse had not fed me when I was a child, I should not have been able to conduct any of those enterprises which I now carry on, both with my head and with my hand, nor should I ever have obtained the fame which is due to my labours both in peace and war; would you on that account argue that the services of a nurse were more valuable than the most important undertakings?