What can science prove?

[Caecilian]

But they don't form some sort of entity, as you find in Freud

Is this also a matter of debate?

It depends on which circles you move in. Since the 'Cognitive Revolution' of the 1950s, Anglo-American Philosophy of Mind/ Cognitive Science has drawn its empirical evidence from experimental Psychology and from Neuroscience. Thats because these disciplines are scientific- they run replicable experiments and construct models based on the results of replicable experiments.

By contrast, the 'evidence' of the Psychoanalytic school (Freud, Jung, Adler and their successors) consists of analyst-patient interactions. These are much more ambiguous, not replicable and very prone to being influenced by the theoretical preconceptions of the analyst.

Unfortunately for Psychoanalysis, the sort of picture that emerges from Cog Psy and the Neurosciences bears very little resemblance to Freud. Thus the psychoanalytic ontology of 'ego', 'super-ego', 'id', 'the unconscious' etc has zero respectability in contemporary Cog Sci.

OTOH there are still plenty of Freudians around. Perhaps ironically, Freud has had a major impact on Continental Philosophy, Lit Crit and other disciplines where scientificity isn't so much of an issue. I say 'ironically' because Freud himself conceived of Psychoanalysis as a type of science.