When I was writing my book The Happiness Project, I identified my “Eight Splendid Truths” about happiness. Figuring out these “truths” took years of study and reflection, because I had to figure out how to think about happiness.

Happiness is a tricky concept: it’s abstract, complex, and everything feels tangled up with everything else.

In the end, I identified eight fundamental principles of happiness. The principle that took me longest to understand became my “Second Splendid Truth.”

This truth comes in two parts, which interlock in a way that confused me for a long time.

Here it is:

One of the best ways to make yourself happy is to make other people happy;
One of the best ways to make other people happy is to be happy yourself.

People often focus on the first half of this statement—which is absolutely true and one of the nicest things about human nature. One of the best ways to make yourself happy is to make other people happy.

Some people believe that the fact that you get “credit” for a worthy act somehow minimizes its worth, and along the same lines, some people argue that you can never act with true altruism, because performing good acts bring the pleasure of happiness. My view: all the better!

The fact is, the sight of someone performing a generous or kind act always makes me feel happy. Especially if it’s me! The spectacle of virtue inspires the feeling of elevation—one of the most delicate pleasures that the world offers. As Simone Weil observed, “Imaginary evil is romantic and varied; real evil is gloomy, monotonous, barren, boring. Imaginary good is boring; real good is always new, marvelous, intoxicating.”

Yes, one of the best ways to make yourself happy is to make other people happy.

And the second part of the Second Splendid Truth is equally important: One of the best ways to make other people happy is to be happy yourself.  Happier people tend to make people happier. We can’t make someone be happy, but our own happiness often rubs off on other people.

People often focus on the first half or the second half of the Second Splendid Truth, or they imagine that we must choose one course, but in fact, we should remember the entire truth of that statement. They don’t contradict each other, they reinforce each other.