Much of the theory of rational materialism derives from the notion of nature -- as in the nature of man, the nature of the universe, or as a natural law. The rationality of their argument hinges upon the belief, nay the faith, that their principles are universal and natural - inherent in the object of their discourse, not merely in the discourse itself.
And the nature they perceived in mankind has not always been a pretty sight. They perceive themselves in a perpetual struggle to survive at odds with all other persons struggling to survive, and the survival of each depended upon strength and cunning relative to the other. (note: these theories precede Darwin, and they are of the same culture) Two granddaddies of the social theory of materialism - packaged today as economics - were the Englishmen, Hobbes and Townsend.
Hobbes argued for a tough governing order to maintain civil order. Townsend championed the laissez faire - the notion that there are natural forces at work to maintain order- i.e, starvation - such that no state intervention is required. In either case, it did not behoove anyone to "abet the enemy" as it were, by providing assistance to those in need. Jeremy Bentham, following the debate concluded: "In the highest stage of social prosperity...the great mass of the citizens will most probably possess few other resources than their daily labor, and consequently will always be near to indigence... (therefore) the task of the government was to increase want in order to make the physical sanction of hunger effective" (Bentham quoted in Polanyi)
This beast-like view is culturally perpetuated, as witnessed in the entertainment industry, video games, in classrooms and the nightly news. But is it really our nature?
Looked at from a very narrow view, all of us are engaged in a self-interested motive to survive. We are born, we live a life of stress and struggle, and then we die. From this view, life is very tragic, indeed. With a little broader view, we include our ancestors and descendents into the picture. Then we see the continuation of technology and arts, material well-being, living beyond our own feeble frame and giving a worth to all the struggle and stress; and so we may die with some satisfaction leaving our attachments with those to whom we are attached. At a greater scope, we may have a belief in a God or some other just restitution - a final release from our limited view after death. We feel that this will invest meaning to our life.
Still this is a limited scope. It is concerned with one life, one death, and only those closely connected to it. At a broader scale - a universal scope - one can see that beings live, beings die. This body dies; this body is born. What we see when we view beyond a narrow attachment to self is a vast harmony; a balance. All of us eat to live; my exhale is our inhale and vice versa; we also defecate fairly regularly and eventually give up the ghost to others. One can view this process as a struggle, or as a reciprocity of being. You can view your being on this planet as a inherited treasure to be protected from all other beings, or as a great debt to all other beings for allowing you to be. This is a greater scope.
But still we are discussing view, not nature. Rational Materialism presumes that we can really come to an objective knowledge of things by viewing them "objectively," i.e., as mere objects, like isolated bits of matter. And yet, if we really look into these hard discrete material building blocks - called matter - if we really analyze down to their nature, we really don't find anything. At least, not anything isolatable and hard. It is really more like a systemization of energies or forces - as in probability waves - giving rise to temporal patterns in space. These are perceived by a consciousness as various shapes, textures, colors, sounds, etc., and they are imputed with meaning by intellect. Things as such - as what we experience - are inseparable from view.
Nature - as an objective, absolute or ultimate reality - is knowable only when consciousness transcends its own narrow view: as when the knower, the knowing and the thing known are identical. This is the Orient's view of Enlightenment. In the Occident, on the other hand, "Enlightenment" is applied to the fall of the Church, the rise of market-economy, and the deification of ego and rationality. The modern paradigm is the liberalization, not the transcendence of view; it is in no case ultimate or objective. It more like the view through a multifacted crystal: the more individuated, the more facets. We cannot find its nature without first admitting and then examining the nature of mind itself.
"If, to Hobbes, man was as wolf to man, it was because outside of society men behaved like wolves, not because there was any biological factor which men and wolves had in common. .... But on the island of Juan Fernandez there was neither government nor law; and yet there was balance between goats and dogs.... No government was needed to maintain this balance; it was restored by the pangs of hunger on the one hand, the scarcity of food on the other. Hobbes had argued the need for a despot because men were like beasts; Townsend insisted that they were actually beasts and that, precisely for that reason, only a minimum of government was required. ... No magistrates were necessary, for hunger was a better disciplinarian than the magistrate.... " (Polyani, 1947; pp 114, 115)