The key concepts in Morya’s Cosmological Notes are: “space” and “essence.” or —
 The nature of space.
 The nature of matter.
By space what is being referred to? Is it ākāśa or śūnyatā? When the notes refer to the eternal space, or “the one element,” the Skt. term धातु dhātu is meant. This term is said to be older than the term śūnyatā.
“‘What is that which was, is, and will be, whether there is a Universe or not; whether there be gods or none?’ asks the esoteric Senzar Catechism. And the answer made is—SPACE.” (The Secret Doctrine, Vol. 1., 1888, page. 9)
This can be compared with the Saṃyutta-nikāya —
“Whether there is an arising of Tathāgatas or no arising of Tathāgatas, that element [dhātu] still persists, . . .” (Bhikku Bodhi, The Connected Discourses of the Buddha: A Translation of the Saṃyutta-nikāya, vol. 1, 2000, p. 551)
“(5) What is the one eternal thing in the universe independent of every other thing?
“(6) What things are co-existent with space?
“(iii) Motion, for this is the imperishable life (conscious or unconscious as the case may be) of matter, even during the pralaya, or night of mind.
“When Chyang or omniscience, and Chyang-mi-shi-khon – ignorance, both sleep, this latent unconscious life still maintains the matter it animates in sleepless unceasing motion.” …
“In short, motion, cosmic matter, duration, space, are everywhere and for perspicuity’s sake, let us place or fancy this multiplicity in or at the top of a circle (“boundless”). They are passive, negative, unconscious, yet ever propelled by their inherent latent life or force.”
– Morya, “Cosmological Notes” to A.O. Hume.
The second key topic is matter, or substance. We refer to it in the Skt. term as प्रकृतिः svābhāva, or rather mūlaprakṛti. Firstly, theosophy rejects the idea of absolute chance, or svābhāva as ahetu; and in many cases, this term has been historically used to refer to a pure accidentalism of life’s actions, even fatally rejecting law of causality. So, another corresponding term is mūlaprakṛti, and in Chinese philosophy, as tzu hsing, the primary germ, or self-originating (tzu-jan) nature out of which the world evolved. This concept of svābhāva (prakṛti), as essence, or “primary substance” in this philosophy is a fundamental subject of study for the student.