Laughter is a compilation of three essays by Henri Bergson on the concept of joy and laughter and its role in human society. Over the course of the book, Bergson breaks down why humans laugh and how laughter has served our development as a species.

The attitudes, gestures and movements of the human body are laughable in exact proportion as that body reminds us of a mere machine.

Bergson asserts at the beginning of the book that motion and contrast are essential aspects of laughter and comedy, stating that the contrast between rigidity and movement leads to the creation of comic situations. The idea of a man falling down in a crowd and being laughed at comes from the juxtaposition of the motion of the man with the relative rigidity of the crowd, as well as the absurdity of the man functioning "improperly." This is why Bergson states that we are entertained when we are reminded of machinery in motion, because it seems humorously inhuman.

What, then, is requisite to transform all this into a comedy? Merely to fancy that our seeming freedom conceals the strings of a dancing-jack . . .

Bergson states that everything serious in this life is derived from our freedom. We can be stalwart and serious in our decisions because we feel we have control over them. Humor is derived from the perception that we have no true control over our actions—instead, we are simply "puppets." This absurd situation can be seen in the humor of seeing a child think they have the decision-making ability to improve upon their parents' decisions. When people observe the world and believe that they have absolute freedom and are making the best decisions for themselves, but then glimpse the futility of their actions and the falseness of their sense of control, they can laugh at themselves and their immaturity.

Comic absurdity is of the same nature as that of dreams.

Near the end of the work, Bergson puts forth the idea that comic absurdity reflects the absurdity of dreams. Logic is foolishness, and when one observes it in the context of the real world, it falls apart into laughable stupidity. Essentially, Bergson posits that comedy occurs when one tries to apply some logic or skill to a situation and fails miserably—like in dreams, where the dreamer may find themselves severely lacking in logical understanding or motor skills but takes action anyway. Once again, comedy arises from the juxtaposition of rigidity (the correct action, or logic) and motion (a hopeless attempt to do the right thing, like trying to stabilize oneself by wildly flailing one's arms).