What is he? Sitting there. His face contorts: the eyebrows rise, the lips curl. He waits.

And I know what he expects so I oblige: making faces and waving my arms and devolving into a spinning fan of nonsense syllables and smiles.

He opens his mouth in appreciation, and waves his fists, and drops his chin and laughs and cackles and shrieks.

It worked, again. Success. He laughs.

But why?

It’s not random at this point: he awaits me, he knows I have it in me to make a fool of myself at his request. We communicate through his laughter, and his anticipation of it, and my love of it.

He makes me make him laugh, and then I laugh, too.

Again, though, why?

Some say laughter is the human reaction to realizing that some threat has vanished; fear rises within us, but when the bogeyman morphs into merely a shadow or a witch’s cry has only been the wind, the fear turns to laughter and release.

But my son is not afraid of me. He tells me this when he glows, upon seeing me come home at the end of a work day. He assures me of this when I swing him through the air, or when he sits on my lap to read with me, and then tilts his head back to see my face and make sure I’m still there.

So his laughter must mean something else.

Aristotle thought it marked a juxtaposition: we laugh because we see a living contradiction. Maybe this is what James sees: an apparently stolid, serious father transforming before his eyes into a clown.

Maybe William James and Carl Lange were right, that our bodies betray our seriousness and we laugh before we understand why. Emotion begins in the muscles and joints and spreads to our mind last of all. We smile before we know we’re happy, and we laugh only to realize we’re entertained.

I like this idea best: because it means that the laughter is deeper in our hearts than it is in our heads. Laughter comes packaged with the soul and the mind’s interpretation of it is only peripheral to its operation. Laughter is as real and solid to him as mass and extension.

Perhaps Descartes can guide us through. To borrow from the Frenchman, maybe James laughs as proof that he is a laughing thing. He laughs because he realizes for a moment that he is a figure to be made to laugh. He laughs because he is safe and because he is happy and because he is noticed.

And I laugh for those same reasons. My guard has dropped, my self-consciousness has receded, and I remember what it is to be artless and guileless and to live only for the unmixed joy of living.

The corners of the mouth tell us the truth about ourselves and each other. James knows this, and he laughs to assure me that he understands the important things. He knows that I will always laugh with him, and to him, and for him.

I laugh that it can be this simple.