Below is an excerpt from Rudolf Steiner's book, "Theosophy: An Introduction to the Spiritual Processes in Human Life and in the Cosmos." 1994. Anthroposophic Press: Hudson, New York. Pg. 96-99.
"Within our body, our eyes and ears develop as organs of perception, as senses for bodily processes. Similarly, we can develop soul and spiritual organs of perception that will open up soul and spirit worlds to us. For anyone who does not have such higher senses, these worlds are dark and silent, just as the physical world is dark and silent to a being without eyes and ears. However, we relate differently to these higher senses than to our physical ones, which as a rule are fully developed in us by good Mother Nature without our doing anything about it. But we ourselves must work at developing our higher senses. Just as nature develops our physical body so that we can perceive our physical surroundings and orient ourselves in them, so we must cultivate our own soul and spirit if we want to perceive the soul and spirit worlds.
There is nothing unnatural about cultivating the higher organs that nature itself has not yet developed, because in a higher sense, everything that human beings accomplish also belongs to nature. Only those who contend that we should all stay at the level of development where nature left us could call developing these higher senses "unnatural." For such people, these organs and their significance are "mis-known" in Goethe's sense. Such people might as well oppose any and every kind of education for human beings---because that too goes beyond the work of nature---and should also be especially opposed to operating on anyone who was born blind. What happens to a blind person after a successful operation is very much like what happens to those who awaken their higher senses in the way described in the last section of this book. The world now appears to them full of new qualities, new processes and new facts that their physical senses never revealed. They see clearly that there is nothing arbitrary or capricious about supplementing reality through these higher organs, and that without these organs the essential part of this reality would have remained hidden from them. The soul and spirit worlds are not "next to" or "outside" the physical world, not separated from it in space. The formerly dark world is suddenly radiant with light and color for a person born blind who has undergone an operation. Similarly, the soul and spiritual qualities of things that until now had appeared to us only in a purely physical way are revealed when we are awakened in soul and spirit. Of course this new world is also full of occurrences and beings that remain totally unknown to anyone who has not undergone a soul and spiritual awakening. (Later on in this book, the development of the soul and spiritual senses will be discussed in greater detail, but first the higher worlds themselves will be described. Those who deny the existence of these worlds only demonstrate that they have not yet developed their own higher organs. Human development is never complete at any given level; it must always be taken further.)
We often tend, unintentionally, to imagine these higher organs as being too much like our physical ones. It is important to remember that these organs are soul or spiritual formations and that we must not expect what we perceive in the higher worlds to be only a misty and diluted form of material substance. As long as we expect anything of that sort, we will not come to a clear idea of what is actually meant here by "higher worlds." Many people would find it much easier to actually know something---at first, of course, only the elementary facts---about these higher worlds if they did not imagine that what they are to perceive is a highly refined version of something physical. That they make this assumption usually means that they do not want to recognize what is really involved. They find it unreal, do not accept it as something that could satisfy them, and so on. True, the higher levels of spiritual development are difficult to reach, but the levels adequate for recognizing the nature of the spiritual world---and that is already a lot---would not be nearly as difficult to reach if people would first get rid of the prejudice that makes them imagine that what is of a soul and spiritual nature is simply a more refined version of what is physical.
We obviously do not really know a person if we have only an idea of his or her physical appearance, nor do we really know the world around us if we know only what our physical senses can tell us about it. A photograph becomes intelligible and full of life to us once we come to know the person in the photograph so well that we know his or her soul, and in the same way, we can really understand the material world only once we know its soul and spiritual basis. That is why it is good to talk first about the higher worlds of soul and spirit, and only then come to conclusions about the physical world from a spiritual scientific point of view."