One-hundred-and-seventy-seven years ago on this date, a 24-year-old Soren Kierkegaard met 14-year-old Regine Olsen and fell in love. He waited nearly three years to profess his love and pop the question — then after just 13 months, grew anxious over the prospect of being a loving, attentive husband and broke things off, completely devastating Olsen. Kierkegaard wanted to make things work but feared his devotion to both Christianity and his work would make for an unhappy marriage, and so he got out while the gettin’ was good and lived the rest of his life a celibate bachelor (which is sort of a self-fulfilling prophecy as he once said, “My melancholy is the most faithful sweetheart I’ve ever had”).

Thinking about love in a philosophical manner can feel a little cold and clinical. The idea that it can be concretely defined and categorized distracts from the unaccountably human component of love and the beautiful, complicated mess it often becomes. Yet, that messiness does run through many philosophers’ ideas on love and the struggle to define what it actually is or does. With that, here are five philosophers’ takes on love:

1. Soren Kierkegaard

Kierkegaard grappled with love most prominently in Works of Love, writing about agape, or unconditional love. For Kierkegaard, the Christian conception of agape is the only true love, for Christian love reveals “that it has within itself the truth of the eternal.” Ever the existentialist, Kierkegaard goes on to write, “All other love, whether humanly speaking it withers early and is altered or lovingly preserves itself for a round of time — such love is still transient; it merely blossoms.”

2. Judith Butler

Butler is skeptical of love, especially the commonly accepted conception of it, writing “… to say ‘I love you,’ of course is to submit to a cliché,” and “In saying ‘I love you,’ a certain ‘I’ is installed in one of the most repeated phrases in the English language, a marketed phrase that belongs to no one and to anyone.” Of course, she’s mainly dissecting the actual sentence here and the complete inadequacy of its words.

What’s more interesting and even beautiful are Butler’s thoughts on commitment to another person. In her eyes, a single instance of commitment — whether symbolically through marriage or otherwise — is an absurd proposition. She believes this because circumstances change, as do people. Commitment, then, should not be a blind, unalterable act but rather flexible and amenable to change, as should both parties in the relationship: “… if commitment is to be alive, that is, if it is to belong to the present, the only commitment one can make is to commit oneself again and again.”

3. Aristotle

Of the classic ideas on love, Aristotle seemed most intrigued by philia, or brotherly love, and the types of friendships contained within it: utility, pleasure and friendships of “good.” Utility friendships are just that: relationships that exist mostly due to circumstance. You may think you and the bagel cart dude are as thick as thieves, but you’re just using each other for cash and cream cheese. Friendships of pleasure go a bit deeper but are solely built around shared interests or hobbies. Friendships of “good,” then, have the most depth and love: a relationship wherein both friends truly appreciate each other’s character — in other words: you’re BFFs.

However, for Aristotle, none of this love and friendship (at least the good kind) is attainable without first achieving self-love: “… the good person must be a self-lover, for he himself will profit from doing fine things, and he will benefit the others.”