Quotes: Son. Song. Space. Spartan.

The sentence in bold face is a plain statement of the quotation that follows.

Son
A son is an encumbrance.
Son 71 “I have spoken to you as I would to my own son, if I had such an encumbrance.” Hawthorne, Fanshawe

Metaphor for a father and son.
Son 61 Though I was his son he knew me only as one lamp is briefly lit from another in the windy night. Eiseley, The Star Thrower

Song
What is too subtle, deeply felt, revealing or mysterious cannot be said, but can be sung and only sung.
Song 243 …what is too subtle to be said, or too deeply felt, or too revealing or too mysterious—these things can also be sung and only be sung. Clark, Civilization.

Space
Forces in the world have been reduced to space, time, matter, energy and gravitation; matter and energy are equivalent and space and time are indivisible.
Space 103 The first long advance [in science] was the reduction of the world’s multifarious substances into some 90 natural elements...these elements were reduced to a few fundamental particles...the various “forces” in the world came to be recognized one by one as varying manifestations of electromagnetic force, and all the different kinds of radiation in the universe--light, heat, X-rays, radio waves, gamma rays--as nothing more than electro-magnetic waves of varying length and frequency...the features of the universe distilled down to a few basic quantities--space, time, matter, energy, and gravitation...in Special Relativity, Einstein demonstrated the equivalence of matter and energy, and in General Relativity he showed the indivisibility of the space-time continuum. Barnett, The Universe and Dr. Einstein

Spartan
A Spartan was part of a machine with the purpose of killing or being killed.
Spartan 176 A Spartan was not an individual but a part of a well-functioning machine which assumed all responsibility for him, exacted absolute submission from him, molded his character and mind, and imbued him with the deep conviction that the chief end of man was to kill and be killed. E. Hamilton. The Greek Way.