Neither a person nor a nation can exist without some higher idea. And there is only one higher idea on earth, and it is the idea of the immortality of the human soul, for all other "higher" ideas of life by which humans might live derive from that idea alone.
Ill-digested principles are, if anything, worse than ill-digested food, for the latter harms the body and there is cure for it, whereas the former ruins the soul and there is no cure for it.
If we state the function of man to be a certain kind of life, and this to be an activity or actions of the soul implying a rational principle, and the function of a good man to be the good and noble performance of these, and if any action is well performed when it is performed in accordance with the appropriate excellence human good turns out to be activity of the soul in accordance with virtue, and if there are more than one virtue, in accordance with the best and most complete.
It's prudent to gain the whole world and lose your own soul. But don't forget that your soul sticks to you if you stick to it; but the world has a way of slipping through your fingers.