Strength is a virtue. It is not merely an attribute that allows good people to do good, and evil people to do evil. A good man who is weak is less good than he would be if he were strong. The evil man who is strong is, though still evil, at least not wholly lacking in redeeming qualities.
This is the classical, Greek view of physical strength.
Modernity takes an antagonistic view of strength, generally looking down upon strength as, at best, superfluous. Many see strength as an overcompensation, or worse, a tool for the execution of evil.
In Starting Strength, Mark Rippetoe concisely and efficiently upends this modern paradigm. But he is not a pure classicist either. He goes beyond the Greek conception of strength as a virtue, instead viewing it as the virtue. "Physical strength is the most important thing in life," begins Chapter 1. He cites not only the happiness and health that come from being strong, but the existential necessity of performing the physical labor our bodies were designed for. In lieu of hauling around 200 lb animal carcasses or hurling javelins at foes, we in the modern, industrial world are the possessors of bodies designed for serious physical exertion. Built into this design is an appetite, and without feeding this hunger, we will not feel normal.
Strength training feeds that hunger.
Far from a mere philosophical treaty on the importance of muscle-mass, Starting Strength is first and foremost a technical manual on building strength. Rippetoe is not concerned with appearance, nor is he focused on the health-benefits of being strong, although he acknowledges that these usually follow from being stronger. His purpose is purely upon the development of strength, and his book synthesizes a surgeon's anatomical knowledge of the body with a lifetime athlete's experience.
Starting Strength advocates the use of integrated barbell exercises, including the squat, the press, the deadlift, the bench press, and the power clean. Especially high value and attention is placed on the squat: "[t]he full-range-of-motion exercise known as the squat is the single most useful exercise in the weight room, and our most valuable tool for building strength, power, and size."
Ultimately, barbell training may not logistically be within everyone's reach. That is not an excuse not to train, as there are other means of acquiring and maintaining strength than without expensive equipment or access to a fully-equipped gym. But barbell training should be a target for everyone who has the means to pursue it. Barbell training is not the only way to acquire strength, but it is the best way.
And everyone should desire strength.
"There is more wisdom in your body than in your deepest philosophy."
- Friederich Nietzsche