The basic Empedoclean model, according to which everything (humans included) is comprised of four elements (earth, air, fire, and water), or "roots" as he called them, and two forces, namely “philia” (love/attraction) and “neikos” (hate/repulsion), as he called them; the logic of which was upgraded by Goethe in 1809, via Torbern Bergman stylized affinity chemistry (physical chemistry) plus metamorphology (evolution) explanation; the third upgrade of which, i.e. Gibbs and Goethe connection, namely the re-interpretation of "affinity" in terms of Gibbs energy is an upgrade in progress, one very intricate.

“Water has a greater affinity with wine, but with olive oil it is unwilling to mix.”

— Empedocles (c.450BC), fragment 56 (B91); Philoponus, Commentary on Aristotle’s Generation of Animals, 123.19-20 [1]

“And that,” interrupted Edward, “will be different according to the natural differences of the things themselves. Sometimes they will meet like friends and old acquaintances; they will come rapidly together, and unite without either having to alter itself at all—as wine mixes with water. Others, again, will remain as strangers side by side, and no amount of mechanical mixing or forcing will succeed in combining them. Oil and water may be shaken up together, and the next moment they are separate again, each by itself.”

— Johann Goethe (1809), Elective Affinities (P1:C4)

“The fundamental unit of affinity in the whole of nature, from the simplest chemical process to the most complicated love story, [as] was recognized by Empedocles [and] Goethe, [can be] reduced, on logical analysis, to matter (space filling substance) and energy (moving force), [which] are but two inseparable attributes of one underlying substance.”

— Ernst Haeckel (1895), The Riddle of the Universe [7]

“Has not Goethe, following Empedocles, told us how carbon and oxygen love each other, how passionately they fly, lover-like, into each other's arms? The union is extremely firm, as is testified by the quantity of heat evolved by a fire during the process of combination, and by the chemist's great difficulty when he seeks artificially to undo it.”

— Caleb Saleeby (1904), “The Green Leaf” [2]

“These elements are equal, all of them, and of like ancient race; and one holds one office and another and each has his own nature”—some being predominantly warm, others cold. They were coeval and eternal—for if they perish whither should they go? (Fragment 87.) "From these arose blood and various kinds of flesh" (203), “and if your faith be at all lacking in regard to these (elements), how from water and earth and air and sun (fire) when they are mixed arose such colors and forms of mortal things,” the attraction and repulsion of modern physical chemistry, symbolized under the conception of love and hate accomplished it, a simile carried out in the meaning of Empedocles by Goethe in his wonderful novel Elective Affinities (Die Wahlverwandtschaften). Combinations of the elements arose under “the uniting power of Aphrodite” (210). He seems to have thrown much, if not all, of his written work into the form of poetry and his other physical ideas as well, are full of poetical conceptions even in the reports and traditions of later writers. So Goethe made poetry of the Metamorphosis of Animals and Plants.”

— Jonathan Wright (1920), “Empedocles the Primitive Physiologist” [3]

A snippet of Jurgen Mimkes on Goethe and Empedocles, from his “Interactions of Heterogeneous Agents in Stochastic Socio-economic Systems”, presented at the 2003 7th annual Workshop on Economies with Heterogeneous Interacting Agents; at the end of which he mentions Wolfgang Weidlich (1971). [9]

“The idea [of society as a many particle system] goes back to Empedocles who in his On Nature explains the solubility of wine in water by the attraction of love of relatives, the segregation of water and oil by the hate of enemies. Goethe used this idea in his Elective Affinities to demonstrate that human relations depend on the chemical laws of society.”

— Jurgen Mimkes (1997), “Society as a Many Particle System” [4]

“The reinterpretation of the process of combustion requires the very elements of chemistry—literally and figuratively—to be ordered anew. For the new conception no longer permits the notion, maintained by the philosophers, alchemists, and chemists since antiquity, that all matter consists of admixtures of four elements joined by attraction and sundered by repulsion—or, as Empedocles would have it, by love and hate, thus anthropomorphizing matter in a way that turned out to have great resonance for Goethe.”

— Michel Chaouli (2002), The Laboratory of Poetry [8]

“Relatives mix like water and wine; enemies avoid each other like water and oil.”

— Jurgen Mimkes (2005), “Chemistry of the Social Bond” [5]

“People who love each other mix like water and wine; people who hate each other segregate like water and oil.”

— Libb Thims (2007), Human Chemistry [6]