|A depiction of 30 types of feelings made by Jim Borgman. |
In hmolscience, in the context of pure materialism and reductionism, when one follows the descendency of evolution downward to the pure atomic, chemical, molecular level, the equation of how “feelings” are explained within this framework often comes to the fore.
In 1874, English physical economist Stanley Jevons gave the following view of "feelings" in the context of the scientific method, reductionism, materialism, evolution, heat death, heat birth, thermodynamics, in relation to the human heart: 
“By degrees it is found that the chemistry of organized substances is not widely separated from, but is rather continuous with, that of earth and stones. Life itself seems to be nothing but a special form of that energy which is manifested in heat and electricity and mechanical force. The time may come, it almost seems, when the tender mechanism of the brain will be traced out, and every thought reduced to the expenditure of a determinate weight of nitrogen and phosphorus.”
“No apparent limit exists to the success of scientific method in weighing and measuring, and reducing beneath the sway of law, the phenomena both of matter and of mind [mind brain duality]. And if mental phenomena be thus capable of treatment by the balance and the micrometer, can we any longer hold that mind is distinct from matter? Must not the same inexorable reign of law, which is apparent in the motions of brute matter, be extended to the most subtle feelings of the human heart [love]? Are not plants and animals and ultimately man himself, merely crystals, as it were, of a complicated form? If so, our boasted free will becomes a delusion, moral responsibility a fiction, spirit a mere name for the more curious manifestations of material energy. All that happens, whether right or wrong, pleasurable or painful, is but the outcome of the necessary relations of time and space and force, and of the laws of matter emerging from them, which are fixed in the very nature of things.
Materialism seems, then, to be the coming religion, and resignation to the nonenity of human will the only duty. Such may not generally be the reflections of men of science, but I believe that we may thus describe the secret feelings of fear which the constant advance of scientific investigation excites in the minds of many who view it from a distance. Is science, then, essentially atheistic and materialistic in its tendency? Does the uniform action of material causes, which we learn with an ever increasing approach to certainty, preclude the hypothesis of an intelligent and benevolent creator, who has not only designed the existing universe, but who still retains the power to alter its course from time to time?”
He concludes this excellent tract, being already well past the 400-page mark of his treatise, by commenting “to enter actually upon theological discussions would be evidently beyond the scope of this work.”
In 1878, Scottish physicist James Maxwell, in commentary on Carl von Nageli, speculating about the "feelings" (or not) of molecules in relation to each other's proximity. 
In 2011, American biophysical chemist Mala Radhakrishnan, published her collected poems book Atomic Romances, Molecular Dances, written over a period of ten years, she frequently incorporates notions who atoms and molecules “feel” into her work: 
“When I think of chemistry, I always think of what are the atoms feeling on a molecular and atomic level and in a lot of ways, the reactions that they experience are similar to the relationships that people experience.”
1. (a) Jevons, William Stanley. (1874). The Principles of Science: a Treatise on Logic and the Scientific Method (Book VI, ch. 31: Reflections on the Limits of the Scientific Method, pgs. 427-70; quote, pgs. 427-28).
(b) Mirowski, Philip. (1989). More Heat than Light: Economics as Social Physics, Physics as Nature’s Economics (pg. 219). Cambridge University Press.
2. Maxwell, James. (1878). “Review: Paradoxical Philosophy”, in: Scientific Papers, II, pg. 451; in Nature, 19 (19 Dec 1878): 141-43; in: Scientific Papers, 2, 756-62.
3. (a) Marder, Jenny. (2011). “Drooling Electrons, Thermodynamics, and Beta Decay … in Verse.” PBS Newsroom, Science Thursday, Nov. 17.
(b) Radhakrishnan, Mala. (2011). Atomic Romances, Molecular Dances (abs). LuLu.com.
4. Feelings (drawings) – by Jim Borgman.
● Feeling – Wikipedia.