At age 17, Aristotle enrolled in the Platonic Academy. He would stay there for 20 years.

Founded by the father of Western philosophy, the Greek philosopher Plato, Aristotle was the most promising student around. He asked many questions and answered even more.

The exact time of his departure from the Academy is disputed, but it’s said that he left soon after Plato died due to his dislike of the direction that it subsequently took. In the years following, he would even go on to argue against many of his late teacher’s core ideas.

It’s impossible to say how much Aristotle wrote, but even from the fraction of his work that we have left today, there is a stunning amount of breadth in the subjects he covered.

Every field from astronomy and physics to ethics and economics has been influenced by the work of Aristotle. For more than 2,000 years after his death, he has remained one of the most widely read and quoted thinkers in the history of our species.

While his impact can still be felt in the many different subjects today, maybe the most accurate of his observations relate to friendship. He saw it as one of the true joys of life, and he felt that a life well-lived needed to be built around such companionship. In his own words:

“In poverty as well as in other misfortunes, people suppose that friends are their only refuge. And friendship is a help to the young, in saving them from error, just as it is also to the old, with a view to the care they require and their diminished capacity for action stemming from their weakness; it is a help also to those in their prime in performing noble actions, for ‘two going together’ are better able to think and to act.”

The accidental friendships

Aristotle outlined two kinds of common friendships that are more accidental than intentional.

The first is a friendship of utility. In this kind of relationship, the two parties are not in it for the affection of one another, but more so because each party receives a benefit in exchange.

It’s not permanent in nature, and whenever the benefit ends, so does the relationship that brought the parties together. Aristotle observed this to be more common in older folks.

An example of this would be a business or a work relationship. You may enjoy the time you spend together, but once the situation changes, so does the nature of your connection.

Similarly, the second kind of accidental friendship is one based on pleasure. This one, however, is more common in people that are younger. It’s the kind of relationship frequently seen among college friends or people who participate on the same sports team.

The source of such a friendship is more emotional, and it’s often the most short-lived of the relationships. It’s fine for as long as the two parties gain enjoyment through a mutual interest in something external, but it ends as soon as either tastes or preferences change.

Many young people go through different phases in their views on enjoyment, and quite often, the people in their lives tend to change as the phase they’re in recalibrates over time.

Most of the friendships that many of us have fall into these two categories, and while Aristotle didn’t necessarily see them as bad, he did feel that their depth limited their quality.

It’s fine, and even necessary, to have accidental friendships, but there is far more out there.

The friendship of the good

The final form of friendship that Aristotle outlined is also the most preferable out of the three.

Rather than utility or pleasure, this kind of relationship is based on a mutual appreciation of the virtues that the other party holds dear. It’s the people themselves and the qualities that they represent that provides the incentive for the two parties to be in each other’s lives.

Rather than being short-lived, such a relationship often lasts until the end, and there is quite generally a base level of goodness required in each person for it to exist in the first place.

People that lack empathy or care for others seldom develop these kinds of relationships because, more often than not, their preference is to look for pleasure or utility. On top of that, friendships of virtue take time and trust to build. They depend on mutual growth occurring.

You’re a lot more likely to connect at this level with someone when you’ve seen them at their worst and watched them grow from that or if you’ve both endured mutual hardship together.

Beyond the depth and intimacy, the beauty of such relationships is that they automatically include the rewards of the other two kinds of friendship. They’re pleasurable and beneficial.

When you respect a person and care for them, you gain joy from being with them. If they’re a good enough person to warrant such a relationship to begin with, then there is utility, too.

These relationships require time and intention, but when they do blossom, they do so with trust, admiration, and awe. They bring with them some of the sweeter joys that life has to offer.

All you need to know

If you’re someone who has been read for over 2,000 years, there is usually a good reason.

Not everything Aristotle wrote is considered relevant today, and many of his assumptions have since been argued against, but given the originality of his ideas for the time that he lived in, it’s hard not to be impressed by his mind. Few names in history are as influential.

He taught us to examine the world empirically, and he inspired generations of thinkers and philosophers to consider the role and value of ethics in the everyday conduct of our lives.

For the average person, however, the most relevant of his ideas relate to the importance of good relationships. He was particularly curious about the intention of friendship.

While he saw the value in accidental friendships based on pleasure and utility, he felt that their impermanence diminished their potential. They lacked depth and a solid foundation.

Instead, he argued for the cultivation of virtuous friendships built with intention and based on a mutual appreciation of character and goodness rather than on some transactional value.

He knew that such a friendship could only be strengthened over time and that if it did thrive, it would last for life. To Aristotle, few things came close to the value of such a relationship.

It makes sense. At the end of the day, the bonds we forge with those close to us directly shape the quality of our lives. We are, and we live through, the people we spend time with.

For most things, life is long enough. It is, however, too short for the wrong kinds of friendship.

Want to think and live smarter? Zat Rana publishes a free weekly newsletter for 10,000+ readers at Design Luck.

This post was originally published on Medium.