|Basic model of the extrapolate upward approach, wherein one applies the laws and principles of chemistry and physics to explain human behavior.|
“The thought that the dry and forbidding discipline of thermodynamics could be applied to that most theory-defying of all applications, human behavior, may be staggering, and perhaps heresy to some. After all, the purity and precision of thermodynamics has been maintained on the strength of its validity only as a collection of limiting laws for infinitely large systems undergoing infinitely slow changes. However, the interest in thermodynamics has always been based on the great relevance for finite real systems undergoing changes that are fast on our everyday time scale and slow only on the microscopic time scale of atomic motion. Thus we are merely extending the beam of insight from the lifeless behaviors of inanimate matter to the vivid complexities of human behavior. In the final analysis this far-reaching analogy rests on the fact that the basic elements of the description of atoms, molecules, and matter can be scaled up to the realm of living organisms without changes other than in the complexity of the systems and their behavior.”
Likewise, the extrapolate up approach, in terms of physical chemistry, is well-defined in the following 1808 statement of German polymath Johann Goethe: 
“The moral symbols used in the natural sciences are the elective affinities discovered and employed by the great Bergman.”
In his 1809 Elective Affinities, Goethe concluded that since humans have evolved or 'metamorphosized' over time from smaller chemicals that the very same laws and principles that govern the behaviors and reactions of smaller chemicals, namely affinity chemistry, must also govern the behaviors and reactions of humans, which he viewed simply as larger chemicals
One his faced with these two alternative approaches, i.e. up or down, when attempting to reconcile the view that humans evolved or were synthesized over time through chemical reaction mechanism from smaller molecules (and before that from hydrogen atom precursors 13.7-billion years ago) when tracing the evolution timeline downward.
The school of thinkers who use the extrapolate upward approach include Philip Ball, Sture Nordholm, Libb Thims, David Hwang, Christopher Hirata, to name a few. The simplest example is that employed by Thims, who reasons that since the spontaneity criterion, i.e. the equation ΔG < 0 quantifying a spontaneous reaction, which governs the nature of chemical reactions, is a universal principle, that it must also apply to the human universe; which is the same mode of logic used by Goethe, albeit in terms of chemical affinity A, which equates to the spontaneity criterion via the formula A = - ΔG.
A tool used in the extrapolate upward approach is reverse engineering.
A representative of the middle ground approach might be the circa 1869 discussions of French engineer Francois Massieu, and his effort to explain or understand the dualism issue or soul / body or living / non-living split by splitting apart the water molecule into oxygen and water to see if these answers anything.
Alternatives to the up or down approach, used by many, is to use either (a) the emergence approach (b) the unbridgeable gap approach.
1. Tantillo, Astrida O. (2001). Goethe's Elective Affinities and the Critics. New York: Camden House.
2. Nordholm, Sture. (1997). “In Defense of Thermodynamics: an Animate Analogy” (Google Books), Journal of Chemical Education, 74: 273.