It is fair to say that today much of Freudian theory is not generally regarded as true (though it was believed to be true for most of the twentieth century–ardently so). Nevertheless, I think it would be accepted even by Freud’s contemporary critics (including myself) that his theory might have been true—its truth was at least an epistemic possibility. Moreover, his theory describes a metaphysical possibility: there really could be a mind that satisfies all of Freud’s basic tenets—there is a possible world in which people have Freudian minds. They don’t in the actual world, as we now think, but in a possible world people really might function in the way Freud claimed (Oedipus complex, repression, phallic symbols, jokes, slips of the tongue, etc)—he didn’t describe a metaphysical impossibility. So let us suppose we visit such a world: how should we conceive the minds of the people there?
I mean to be speaking of what Freud called meta-psychology and also the philosophy of mind: specifically, with respect to the question of the unconscious. Freud argues that given his clinical findings, and hence the truth of his psychological theories, we are compelled to regard the unconscious as robustly real and robustly mental.  For example, if we repress our memories and emotions, then the result will be an unconscious mental state—just as mental as a conscious state. This mental state will have all the characteristics of conscious mental states save their consciousness, i.e. availability to introspective knowledge. The mind will consist of two mental systems, conscious and unconscious, but both equally aspects of mind—endowed with intentionality, phenomenology, and functionality (causal and teleological). It turns out that Freud was mistaken in many of his theories of the human mind, but in the possible world we are considering his counterpart is completely right about the minds of thosepeople. Thus Freud’s argument for the psychological reality of the unconscious—its existence and nature—applies to the minds of the possible people in question. There could be such people and, if there were, they would have a vibrant and undeniably mental unconscious. The conscious mind would just be a part of their mind, and possibly a late arrival on the mental scene, with the unconscious mind established earlier in evolutionary history. Accordingly, the philosophy of mind in this world would have to recognize the full reality of the mental unconscious. It would be wrong to limit it to the conscious mind, as if that is all there is to psychology; the study of the unconscious would have a place of equal importance to the subject. This means, among other things, that the mind-body problem spans both parts of the mind; it is not specifically a problem about consciousness. Consciousness adds something extra to the picture, but the unconscious also raises difficult questions about its relation to the body. In this possible world theorists would feel the need to include the unconscious along with the conscious.
However, this is not our world, as we now know.  Still, something like Freud’s position holds: we do have an unconscious, even if it is not exactly as Freud described. Most obviously we have unconscious memories: so the general form of Freud’s position still stands. The many systematic interactions between the conscious and the unconscious encourage the idea that the unconscious is a robust mental system existing alongside the conscious and in no whit less real than it. Freudian theory makes this kind of conclusion vivid, but much the same is true under less extravagant conceptions of the unconscious. Those possible minds have an undeniably mental unconscious, so our actual minds should follow the same general principles, even if they are not quite as Freud described. We could even push this line of reasoning further by stipulating a psychology in which the reality of the unconscious is even more undeniable: in a possible world in which this psychology is realized it would be right to adopt a strongly realist attitude toward the unconscious. For example, suppose people were mainly motivated by monetary greed (surely more realistic than Freud’s sexual theory) but that they officially followed a religion that explicitly forbade such acquisitiveness; then we might expect powerful repression of all pecuniary desires with all sorts of odd side-effects. Suppose these people dreamt of nothing but making money and spending it, that they constantly told jokes about money, and that money-related neurosis was prevalent in their society. Suppose also that as children conscious acquisitiveness was natural and universal, before repression set in: all pecuniary desires and emotions are then ruthlessly suppressed, only to leak out in all manner of strange psychological phenomena. Wouldn’t we have overwhelming reason to suppose that these people have an unconscious mind brimming with thoughts of money, desire for money, and money-related emotions—that their unconscious mind is money-obsessed? They are not aware of these unconscious mental states, by hypothesis, but they exist nonetheless.
The point is that the mere fact of unconsciousness is not enough of a reason to doubt the psychological reality of the unconscious in the presence of strong circumstantial evidence for its existence. Being unconscious is not itself a count against the psychological reality of those states; it all depends on what the surrounding evidence looks like. And if there are possible minds in which the unconscious exists in full gleaming armor, so to speak, then we ought to be open to the possibility that our actual minds harbor just such a lusty and strapping unconscious. The metaphysical possibility of a full-blown unconscious mind should soften us up to the thought that we too are similarly endowed. Our own unconscious may not be as spectacular as those postulated (or it may be!), but it is the same kind of thing. 
 See his careful and well-argued paper “The Unconscious” (1915). He is well aware that he needs to argue that the contents of the unconscious are mental in nature, not merely physical or functional; he even sees the need to rebut the idea that the so-called unconscious is another locus of consciousness existing alongside the more familiar consciousness.
 In fact, I think that we have many separate unconscious minds, each richly endowed (see “The Disunity of Unconsciousness”), but it is important to see that the unconscious is psychologically real even under more conservative views of its scope. Even ordinary memory requires us to accept a robust unconscious mental reality.