Without philosophy the mind is sickly, and the body, too, though it may be very powerful, is strong only as that of a madman or a lunatic is strong. This, then, is the sort of health you should primarily cultivate; the other kind of health comes second, and will involve little effort, if you wish to be well physically. It is indeed foolish, my dear Lucilius, and very unsuitable for a cultivated man, to work hard over developing the muscles and broadening the shoulders and strengthening the lungs. For although your heavy feeding produce good results and your sinews grow solid, you can never be a match, either in strength or in weight, for a first-class bull. Besides, by overloading the body with food you strangle the soul and render it less active. Accordingly, limit the flesh as much as possible, and allow free play to the spirit.
— Seneca, Moral Letters to Lucilius, Letter 15
Physical strength is the most important thing in life. This is true whether we want it to be or not. As humanity has developed throughout history, physical strength has become less critical to our daily existence, but no less important to our lives. Our strength, more than any other thing we possess, still determines the quality and the quantity of our time here in these bodies. Whereas previously our physical strength determined how much food we ate and how warm and dry we stayed, it now merely determines how well we function in these new surroundings we have crafted for ourselves as our culture has accumulated. But we are still animals – our physical existence is, in the final analysis, the only one that actually matters. A weak man is not as happy as that same man would be if he were strong. This reality is offensive to some people who would like the intellectual or spiritual to take precedence. It is instructive to see what happens to these very people as their squat strength goes up.
— Mark Rippetoe, Starting Strength