The story goes, from Boileau to Sainte Beuve and to Baudelaire, that Pascal always had the impression that an abyss was opening up on his left side. So he had a chair beside him on which he could rest his arm and make sure the ground remained solid (see Magnard 1). In the poem "Le Gouffre," the abyss is associated with a kind of wind, like the draft produced by an open window, or the slight movement of the air coming from a cellar. It caresses the skin, and the hairs rise from fear.

Baudelaire's abysses do not only open up in the ground. They appear behind windows. They open up in sleep, where the mind drifts into nightmares. They invert, so to speak, and the sky itself becomes an abyss, wherein one could fall upwards. The strand is the seat of another kind of abyss, horizontal when the passerby gazes at the immensity of the sea, and vertical again, if one ventures on the surface of the water. In the poem, “L'homme et la mer,” the abyss of the sea is symmetrical, the correspondent on the outside, to our own abyss, the abyss that we have in our mind: as deep, secret and bitter.

The image of the abyss comes up over and over again. In a passage from the Fusées, Baudelaire notes:

"Au moral comme au physique, j'ai toujours eu la sensation du gouffre, non seulement du gouffre du sommeil mais du gouffre de l'action, du rêve, du souvenir, du désir, du regret, du remords, du beau, du nombre, etc. J'ai cultivé mon hystérie avec jouissance et terreur. Maintenant j'ai toujours le vertige." (Fusées, 668)

The infinite behind windows, the immensity and the depth of the sea, the unknown of sleep, it is easy to understand how space may turn into an abyss. But numbers? How can numbers become an abyss? There is an infinity of numbers. But it could also be that something about them, their order, the laws which apply to them, may go wrong. In another note, in Fusées, Baudelaire wonders:

“Y a-t-il des folies mathématiques et des fous qui pensent que deux et deux fassent trois ? En d'autres termes, - l'hallucination peut-elle, si ces mots ne hurlent pas, envahir les choses du pur raisonnement?” (Fusées, 655)

In The Interpretation of Dreams, Freud gives an example of a mathematical hallucination. It happens in the dream of one of his patients:

“A man dreams: He is sitting at B——'s (a family of his earlier acquaintance) and says, "It was nonsense for you not to give me Amy in marriage." Thereupon he asks the girl, "How old are you?" Answer: "I was born in 1882." "Ah, then you are 28 years old." Since the dream occurs in the year 1898, this is obviously poor arithmetic.” (The Interpretation of Dreams, 328)

1882 + 28 = 1898 is wrong in our arithmetic. How could the dream make it true? It turns out that the patient is followed in Freud's office by a young woman, in whom he becomes interested. He estimates her to be aged 28. Then 1882 is the year of his marriage. So the dreams seems to say: Marriage + Lady = Now. This is an arithmetic of desire where numbers combine according to new laws. 

That numbers may turn into yet another abyss gives an ambiguity to the last strophe of the poem “Le Gouffre.” After reviewing all the abysses, behind windows, and under the surface of the sea, and that of sleep, or empty space, Baudelaire concludes: 

At first sight, the last line seems to mean that, if we could never go out from Numbers and Beings, we would be saved from the abysses opening around us. However, since Numbers may become an abyss themselves, the line may precisely point to the source of all abysses in Numbers: the poet cannot flee from these Numbers that can go wrong, combine in strange hallucinative laws, and produce a disorder for which there is then no remedy.