"The Hindu theosophy is not a religion; it is a system of philosophy derived from the wonderful Kabbala; the teachings of which, concerning nature's Sympathetic Streams (flowing from the central sun of the universe), led Keely into the path of research which has enabled him not only to "hook his machinery on to the machinery of nature," but to disclose the moving power, the vital principle." [Bloomfield-Moore; What Electricity Is - Bloomfield Moore]
"Theosophy is that ocean of knowledge which spreads from shore to shore of the evolution of sentient beings; unfathomable in its deepest parts, it gives the greatest minds their fullest scope, yet, shallow enough at its shores, it will not overwhelm the understanding of a child." [The Ocean of Theosophy, by William Quan Judge, 1893]
H. P. Blavatsky
"Theosophy is the shoreless ocean of universal truth, love, and wisdom, reflecting its radiance on the earth... Theosophy is divine nature, visible and invisible... Theosophy is the fixed eternal sun... Theosophy is the quintessence of duty." [The Key to Theosophy, by H. P. Blavatsky, 1889]
"Theosophy, in its abstract meaning, is Divine Wisdom, or the aggregate of the knowledge and wisdom that underlie the Universe - the homogeneity of eternal GOOD; and in its concrete sense it is the sum total of the same as allotted to man by nature, on this earth, and no more." [The Key to Theosophy, by H. P. Blavatsky, 1889]
"Theosophy is synonymous with the Jnana-Vidya (knowledge of the Great Knowledge), and the Brahma-Vidya of the Hindus (sacred knowledge, knowledge of the Divinity pervading the universe), with the Dzyan of the trans-Himalayan adepts, the science of the true Raja Yogis (Raja Yoga is the kingly union, the highest form of self-development leading to union with one's Egoic Self). It is the parent stem - the Archaic Wisdom; the Light of Truth; the inner teachings of the Mahayana school of Northern Buddhism. It is something more than simple metaphysics. It is meta-metaphysics, metageometry, etc. or a universal transcendentalism; etc., etc." [Helena Petrovna Blavatsky]
Gottfried de Purucker
Theosophy. A compound Greek word: theos, a "divine being," a "god"; sophia, "wisdom"; hence Divine Wisdom. Theosophy is the majestic Wisdom-Religion of the archaic ages and is as old as thinking man. It was delivered to the first human protoplasts, the first thinking human beings on this Earth, by highly intelligent spiritual Entities from superior spheres. This Ancient Doctrine, this Esoteric System, has been passed down from guardians to guardians to guardians through innumerable generations until our own time; and, furthermore, portions of this original and majestic System have been given out at various periods of time to various races in various parts of the world by those Guardians when humanity stood in need of such extension and elaboration of spiritual and intellectual thought.
Theosophy is not a syncretistic philosophy-religion-science: that is to say a system of thought or belief which has been put together piecemeal and consisting of parts or portions taken by some great mind from other various religions or philosophies. This idea is repudiated by Theosophists, for the simple reason that it is not true. On the contrary, Theosophy is that single System or systematic formulation of the facts of visible and invisible Nature, which, as expressed through the illuminated human mind, takes the apparently separate forms of science and of philosophy and of religion. We may likewise describe Theosophy to be the formulation in human language of the nature, structure, origin, destiny, and operations of the Kosmical Universe and of the multitudes of beings which infill it.
It might be added that Theosophy, in the language of H. P. Blavatsky, is "the sub-stratum and basis of all the world-religions and philosophies, taught and practised by a few elect ever since man became a thinking being. In its practical bearing, Theosophy is purely divine ethics; the definitions in dictionaries are pure nonsense, based on religious prejudice and ignorance." (See her posthumous work, Theosophical Glossary, page 328.) [Gottfried de Purucker, Occult Glossary, page 177]
quotes from Theosophy Online