The system called Tantra has always been regarded as an esoteric and secret way of spiritual practice, not supposed to be accessible to the untrained minds of the masses. The secrecy about the practice consists in the novel outlook of life which the Tantra requires the seeker to entertain, a way of looking at things different from the one in which people are accustomed to see, interpret and evaluate things. The teachers of the Tantra hold that a seeker on this path has to outgrow the usual human outlook and develop a superhuman and divine attitude in respect of the world. Since this would be too much to expect from the common man, Tantra is supposed to be a closed secret, whose gates can be opened only on conditions of specialised training in the mastery of one's mind and senses. The philosophy of Tantra is based on the concept of a dual nature of everything, - duality based on unity.
Nothing is single, but everything is bipolar.
The so-called unity of things is only a form taken by a particular manner of the coming together of two forces, the subjective and the objective, designated as Siva and Sakta , the positive and the negative poles of experience. Scriptures dealing with a subject of this kind state that in the beginning there was a universal Uni-Cell, as it were, known as the Brahmanda , the Cosmic Egg, which split into two, one part of which was the Cosmic Man and the other part the Cosmic Woman. Modern science is corroborating this view when it concludes that in the beginning the universe was like a single Atom, which divided itself into two and then into the multiplicity of the present state of the universe. Since the two parts and their subsequent sub-divisions actually belong to the whole, there is a natural pull exerted by each on the other, both at the cosmic level and its lower multiple forms of descent, even down to the minute atom. The behaviour of the two parts of any single organism is a sort of double attitude of the consciousness of duality and unity at the same time.