The best way to learn mathematics is to do mathematics.
"The body's own defenses can be harnessed to combat cancer."
The selfish gene theory is not a theory about selfishness in the everyday sense. It is a theory about the evolution of behavior.
The only phrase I've ever disliked is, 'Why, we've always done it that way.' I always tell young people, 'Go ahead and do it. You can always apologize later.'