Below is the only known reference to the Law of Inevitability in the writings of Alice A. Bailey (AAB) and Djwhal Khul (DK). Links on these pages of the Laws of Alice A. Bailey are to the online books at the Lucis Trust website.
For a discussion of what AAB means by a “law” please see Alice A. Bailey – What is a Law?
But the relativity of these matters does not really concern us, and the perfection is—from the angle of the human disciple today—exactly what we understand by perfection. The Masters know, however, that a higher, deeper and more intensive manifestation of divinity is potentially possible, but it causes Them no concern or strain, no anxiety or fiery aspiration; They know, as no disciple can know, the workings of the Law of Inevitability. This Law releases the Masters (under the accompanying Law of Service), at the sixth initiation, into a wider field of experience, with all the divine assets and qualities so developed within Them that They know that Their equipment is adequate to the undertaking and that They can, without hesitancy and concern, take the next required steps.
Some quotes on “inevitability“:
“The karma of the disciple. Of this, the disciple knows little and the Master much; with that karma He may not interfere, because growth and development eventuate as the disciple meets the inevitability of events, accepts his karma and works to offset it, actuated by right motive.” -Discipleship in the New Age, Vol. II
“In youth the thoughtless (and all are thoughtless, for such is nature’s way) hold on to life and give no thought to the time when there must be a relinquishment of the hold on physical existence. The young forget, and rightly forget, the inevitability of that final symbolic detachment which we call Death. But when life has played its part and age has taken its toll of interests and strength, the tired and world-weary man has no fear of the detaching process and seeks not to hold on to that which earlier was desired.” -Esoteric Psychology – Volume II
You are welcome to post your comments and understanding of this law.