Samadhi means the oneness of human consciousness with cosmic consciousness. Man’s consciousness is subject to relativity and dual experience. In meditation, there are three aspects: the meditator, the act of meditation, and God (the object of meditation).

Samadhi is final union, which comes from deep, continuous, correct meditation. In this state, the three factors of meditation become one. Just as the wave melts in the sea, so the human soul becomes the Supreme Spirit.

Through Oneness in samadhi, the dualities of human experience disappear. Everything is perceived as only a manifestation of the Supreme Spirit. In this state, the soul can perceive the spiritual ocean with its waves of creation; or see the same ocean transcendentally calm, existing without its waves of creation.

In the first state of samadhi (known as sabikalpa) the yogi, his soul united with the Spirit in deep meditation, becomes so absorbed in the Spirit that he is oblivious of the material and subtler created universes. A somewhat similar experience, on a lower plane, is experienced when one becomes so absorbed in a book, or in thinking, that he is unaware of anything happening around him. This state is not unconscious, for unconsciousness implies both inner and outer lack of awareness. Such unconsciousness is easily induced by drugs, anesthetics, and other artificial means. The full spiritual consciousness of even the lower samadhi, however, can be attained only through the regular, continuous, right discipline of meditation; it has nothing in common with unconsciousness.

The first state of samadhi, in which the yogi finds everything withdrawn and absorbed into Spirit, is known, as I said, as sabikalpa samadhi. The higher and greater state of samadhi is

nirbikalpa, in which the yogi, having realized the Spirit alone without its Creation, perceives the Spirit also, simultaneously, as both beyond Creation and untouched by it, and also manifested in all Creation. Here, one’s consciousness becomes cosmic consciousness. His domain of consciousness now extends out from his body to include the whole universe. He becomes the Ocean of Spirit, simultaneously watching the little bubble of his body bobbing about, as it were, on that sea. His consciousness perceives all motion, and each mutation of life from the circling stars to the fall of a sparrow and the whirling of the smallest electron.

The yogi who has entered this final, highest state of samadhi sees all things also in their subtlest essence: Solids melt into liquid and molten states; liquids into gases; gases into energy; and energy into cosmic consciousness. He lifts the four veils of solids, liquids, gases, and energy and beholds the Pure Spirit underlying them, and thus knows himself as Spirit. He sees how the objective universe in Nature and the subjective universe in each individual conjoin in Spirit. His expanded self merges into the great, spiritual Self; they become one. The spiritual Self, being the first cause, and capable of existing without material manifestation, is infinitely greater than the little, egoic self.

Thus, the negative conception of God, as having nothing in common with human ways, is removed. The yogi, instead of finding a cessation of all life and joy—even a vast void, as unenlightened followers of the Buddha believe—becomes the eternal fountain-head of bliss and of all life. The tiny bubble of laughter becomes the sea of mirth itself. In knowing God one does not lose anything at all: He gains everything!

It should be added that it is still possible for the yogi to fall from the state of sabikalpa samadhi, for, from that lower samadhi, he must return to ego-consciousness. One is freed forever once he attains the highest state: nirbikalpa samadhi.

https://www.paramhansayogananda.com/samadhi/