It is known that his main interests were magic and the theory of war, his first book being a translation of a French military manual, Practical Instruction in Infantry Campaigning Exercise (1884).

[4] Mathers was introduced to Freemasonry by a neighbour, alchemist Frederick Holland, and was initiated into Hengist Lodge No.195 on 4 October 1877.

[citation needed] In 1891, Mathers assumed leadership of the Hermetic Order of the Golden Dawn upon the death of William Robert Woodman.

[4] After his expulsion from the Golden Dawn in April 1900, Mathers formed a group in Paris in 1903 called Alpha et Omega (its headquarters, the Ahathoor Temple).

They have had considerable influence on the development of occult and esoteric thought since their publication, as has his consolidation of the Enochian magical system of John Dee and Edward Kelley.

One of his most notable enemies was one-time friend and pupil Aleister Crowley, who portrayed Mathers as a villain named SRMD in his 1917 novel Moonchild.

Aleister Crowley wrote in his Confessions of the decline of the Hermetic Order of the Golden Dawn, as well as that of MacGregor Mathers.

He lamented what he saw as the irredeemable changes by Waite in his order and MacGregor Mathers's legacy of well-meaning but low-quality leadership in his last years.