‘In the pages that follow I shall bring forward proof that there is a psychological technique which makes it possible to interpret dreams, and that [ … ] every dream reveals itself as a psychical structure which has a meaning [ … ] which can be inserted at an assignable point in the mental activities of waking life’. Thus begins Sigmund Freud's century-defining The Interpretation of Dreams (1900). Sweeping aside occult and transcendental speculations he proposed material continuity between dreaming and wakeful awareness. Research has now confirmed that dreams contribute to daily problem-solving, and cerebral dopamine is implicated across dreaming, seeking, reward, joy, addictions and schizophrenia.

The first psychoanalyst's masterwork inspired French poet André Breton's first Surrealist Manifesto (1924): ‘Freud very rightly brought his critical faculties to bear upon the dream. It is, in fact, inadmissible that this considerable portion of psychic activity [ … ] has still today been so grossly neglected’. The Interpretation of Dreams served as foundation for the surrealist movement despite things having gone badly when Breton had visited Freud in 1921. His ‘Interview du Professeur Freud à Vienne’ (1922) described the host as a ‘little old man with no style, who receives clients in a shabby office worthy of the neighbourhood’. In 1932, having received a copy of Les vases communicants (published in English as Communicating Vessels), Freud confessed to not having read it in full but defended himself against certain ‘impertinences’ in the ‘little book’.

In Communicating Vessels, most polemical of the ‘modern materialist’ poet's slim philosophical trilogy, dream and wakeful awareness are conceived as the unity of two vessels through a capillary. Part I reproaches Freud for being too bashful in sharing his dreams and lapsing into mind–body dualism when he writes that ‘“psychic reality” is a specific form of existence that must not be confused with “material reality”’. Breton then reveals and analyses his own dreams in detail. Part II portrays the aftermath of an intense heartbreak and his subsequent uncanny encounters with several women. Dream-like primary process thinking and ‘objective chance’ dominate wakeful life in the service of desire and the unconscious. The final part rejects the demand by the editor of the French Communist Party newspaper L'Humanité that Breton avoid ‘ideology’ and stick to ‘facts’ in his contributions. For surrealism art is not knowledge as such but the ground for valuing, and poetry becomes the capillary uniting the quotidian with the ‘marvellous dream’. Imagination is that which tends to become real.

An American commentator on Communicating Vessels suggests it is difficult to read because Breton's text reconstructs something of the dreamwork's condensation and displacement. However, tenacious readers may be amply rewarded by alighting on a strangely familiar lucidity, a key surrealist value, which evokes an almost impossible affinity with another French dreamer's treatise: Rene Descartes’ (1596–1650) Meditations on First Philosophy (1641). But whereas the great rationalist mistrusted dreams and the imagination in his search for secure foundations of thinking and knowledge, his surrealist compatriot immersed himself in them to probe feeling and justice. Adapting his method to his aims, Breton's dream was the illumination and emancipation of our (materialist) spirit.