According to the definition of the subject as universal mediation, it is in the nature of the subject, to comprehend itself as a part of the world. Nothing can avoid being assimilated by the subject in its internal replica of the world, and then being transformed into a product, a part of the world rebuilt by the subject. The subject's consciousness is not an exception: it is both the result of natural development and the product of the subject's activity. This active self-construction is one of the distinctive features of subjectivity.

Any thing presented to the subject becomes an object. The very definition of an object implies the subject, and no thing can be perceived without an admixture of subjectivity. We only see the world through our activity, and in relation to it. Historically, this trivial circumstance was reflected in numerous paradoxes and resulted distorted vision of consciousness and a conscious being.

In the most radical forms of subjective idealism, it was declared that, since all we perceive is perceived through our senses, nothing should be considered to exist beyond our sensations, and it would be meaningless to ask about reflection of anything outside the individual subject. This idea lead to obvious contradictions and inconsistencies, which, however, did not much impress the adepts of subjective idealism, who generally preferred to merely ignore them. Indeed, if there is a single individual knowing nothing but his sensations, why should one care for any knowledge at all? If there no other people to communicate with, there is no need in cognition, and all the only existing individual does need to perceive anything at all. There would be no way to learn about one's own sensations, since any such knowledge would already oppose them to the subject as something (at least partially) external to it. The only consistent state of such an isolated individual would be a uniform nothing, with no motion at all. This conclusion is experimentally confirmed through observing people in the conditions of sensory deprivation. In such experiments, after a transitory surge of hallucinatory perceptions, the person tends to seize any activity and fall into a kind of lethargy, somnolence without dreams. Numerous meditation practices used that fact to reach a state of indifference named "nirvana", "enlightenment", etc.

Thus, starting from the impossibility of any knowledge but self-knowledge, one comes to impossibility of self-knowledge as well. In subjective idealism, there is no epistemology of consciousness. Any attempts to speak about self-comprehension in subjective idealism are necessarily eclectic, they always employ logically alien elements. Since subjective idealism does not care for knowing anything at all, such eclecticism often pretended to replace the very idea of knowledge, with meaningless babbling in place of science.

Feeling the utter inadequacy of such an approach in real life, philosophers tried to disguise subjective idealism, pretending to avoid the very question of objective existence by saying that we just cannot know about it, and therefore should not talk of it at all. This attitude appealed to scientists, whose poor philosophical education did not allow to reveal the true face of that school, collectively referred to as agnosticism. The normal indifference of a scientist to anything that cannot be scientifically tested was thus substituted with denial of anything beyond the scientific fact, which is nothing but an eclectic variety of subjective idealism merely extending the physiological senses of an individual subject to the instrumental data and formal conclusions constituting the senses of the academic community as a collective subject. The agnostic consciousness is not entirely blind, like that of subjective idealism, it is only strongly myopic.

A much more consistent view was put forward by objective idealism. In this philosophy, the whole world is declared to be a product of some supreme subject, differently named by different philosophical schools: the absolute spirit, God, the supreme will, the fate, karma, Tao etc. All objective idealism is essentially about the same: first, the world gets created by the subject, and then it becomes comprehended by it, thus restoring the unity. In this case, cognition is a kind of self-cognition, and the world is certainly comprehensible, and the subject can cognize itself, through its outer products. In objective idealism, the extension of the individual to collective subject takes its ultimate form, and any subject at all is considered as a manifestation of the absolute, universal subjectivity.

In this philosophy, one can logically admit science, and speak about studying the world. Any partial subject can do research and discover things and other subjects. Individuals can communicate their knowledge to other individuals and establish common conceptual frameworks. Objective idealism perfectly matches the commonly perceptible process of producing things and learning thing produced by the others. On a certain stage of social development, when people become less dependent of nature than from other people, they become tempted to consider their cultural environment as the only environment one can ever have, and every thing seems to be made by somebody. If there is nobody human to create it, a non-human entity is fantasized, which is beyond human comprehension, but which is still felt to be somehow related to human activity.

The problem with objective idealism is that there is no way to tell, why that absolute entity creating the world is necessarily a subject. There is nothing subjective about it, it exists regardless of any other subjects and develops according to objective laws. Why should we call it a subject? Why not simply admit that this is the world in general, which develops through numerous partial manifestations, including its manifestation to the conscious subject, nature? Consistent objective idealism is a direct way to materialism, since the very assumption of an objective process of spiritual development admits an object prior to any spirit, and the only logical continuation is to reverse the scheme and start with the object (nature), deriving the subject (spirit) from nature as a result of natural development.

Materialism, in contrast to idealistic philosophies, tried to describe the world as existing regardless of human activity, and those who have to do anything practical will necessarily act as spontaneous materialists, to be successful. The most convinced idealists immediately become quite materialistic, when it comes to food and shelter, to health and wealth. A solipsist, who writes the books on that there is nothing in the world but his imagination, will call a real doctor at a slightest uneasiness, and a real policeman to defend himself of a street robber. This most ancient kind of materialism governed the work of many scientists ever since science has separated itself from the arts and philosophy, constituting a relatively independent cultural sphere. The scientist believed that there is an object to study, and the subject, who studied the object, producing a commonly acceptable way of treating objects, knowledge. The main goal of science was called "truth", and the truths (facts) had to be discovered, presuming their pre-existence in nature. Once discovered, a fact could not change, becoming a little stone in the huge pyramid of absolute knowledge.

The scientists could easily remain within that primitive philosophy on the early stages of the development of science, when it dealt with relatively simple things. However, as soon as scientific inquiry has reached the domain of very complex motion and development, the traditional scientific objectivity failed to adequately explain phenomena, and the self-confidence of a spontaneous materialist was shattered, when research became indirect and less intuitive. And the epistemology of consciousness became the first and heaviest stumbling block for natural scientific materialism.

Since consciousness was thought to be a natural property of an individual, materialists tried to attribute it to some particular organ, or to distribute it between the organs of the human body. The ancient theory of four temperaments attributed modes of human behavior to the proportion of the four fluids: blood, bile, black bile and phlegm. In the beginning XX century a similar approach became rather popular, taking the form of the James-Lange theory of emotions, psychological behaviorism etc. By the end of the XX century, a philosophical school known under the name of "consciousness science", despite many criticisms, established itself as a standard of scientific methodology in any consciousness studies. In this school, subjectivity was believed to be a function of the brain, and only the study of cerebral processes was recognized as "scientific". Logically, this implied that consciousness should be genetically pre-determined, and the origin of mental disease was sought in bad inheritance. Official psychiatry believed in powerful chemicals as the only cure for psychotic patients, and medicine was often sacrificed to the profits of pharmaceutical companies.

However, scientists felt that such a reduction of the subject to mere physiology did not solve the problem, but rather pushed it out of sight. These doubts took the form of paradoxes (L.M.Vecker):

— Ontological paradox: higher level psychological phenomena cannot be described in terms of lower level mechanisms. In particular, no psychological phenomenon corresponds to a unique physiological pattern, and no physiological process is unambiguously associated to a specific psychological effect.

— Epistemological paradox: people's perceptions and intentions are always expressed in terms of outer objects rather than physiological or psychological characteristics. We observe outer things, rather than our feelings, and our goals are things outside us. Even reflecting on our own moods and feelings, we do it as if they did not belong to us, and perception of a feeling is different from feeling itself. This was metaphorically described as if we had a homunculus inside, who observed our conscious actions and reported them to us.

— Ethical paradox: consciously perceiving ourselves, we change ourselves and thus make our perception obsolete. As soon as we have established a law of mental dynamics, we can consciously violate this law through an outer activity specially directed to that change. It seems like, in the science of consciousness, there can be no final truth, or universal laws, and all we can know is limited regularities.

These paradoxes were often used to "prove" the insufficiency of scientific materialism and the inevitability of idealism, at least when consciousness and subjectivity are concerned. However, as it is usual with paradoxes, they are due to an artificially narrowed view, inadequately applied to a wider area, where wider notion should be used. The ontological paradox is easily solved admitting that reality is always hierarchical, with higher levels providing a general context for lower level processes, and the inverse influence, from lower to higher levels is possible on the average. Each higher level process can be represented by many lower level implementations, neither of them being better than another. Inversely, very different configurations on the lower level can correspond to the same higher level state. The very difference of "the lower" and "the higher" is relative, and depends on the context.

The epistemological paradox is due to the illegal identification of the conscious subject with the physiological body of an individual. As soon as we admit that consciousness is the attribute of both the organic and inorganic body of a person, there is nothing strange in that the inner states of the subject are expressed in terms of common things. Consciousness does not belong to the subject; rather it is a way of the subject's involvement in objective processes. This makes our inner states observable to other people and ourselves. Since any individual is considered as a part of the society, the subject becomes hierarchical; any self-perception is mediated on different levels by the society, and the true "homunculus" can be easily found outside rather than inside us, in the people surrounding us. We see ourselves by the eyes of the others, and nobody else can tell us who we are.

The ethical paradox is trivially resolved considering knowledge as a hierarchy and taking it in development, rather than statically, as huge heap of unchangeable truths. Any truth is relative since it can only exist in a specific cultural context. However, any truth is also absolute in that it will always be true in that context, and the corresponding piece of knowledge will be applicable every time when certain aspects of that context become culturally reproduced. In particular, due to the hierarchical organization of the culture, old truths can reign on some deeper levels of hierarchy, even though the overall behavior has long since evolved to something entirely different. Specifically, when we comprehend ourselves, the hierarchy of the subject grows, and we indeed know ourselves, though only in certain respects. More knowledge comes with time, and there is nothing that cannot be learned.

Therefore, there is no need to appeal to any incomprehensible entities in studying subjectivity, and the materialistic picture of the subject as a part of the self-developing world provides a consistent and uniform platform for any science, including the science of consciousness.