BVSR is itself a variation on common-sense and ancient notions of trial-and-error, and it seems directly inspired by the two-step process of biological evolution, but Campbell sees it as more general than these. BVSR is applicable to organic evolution, the learning process in individual organisms, and the social construction of knowledge.

BVSR can be applied to our two-stage model for free will. Other biological examples include the immune system and quality control in protein/enzyme factories.

The idea that units of cultural knowledge undergo variation and then are selected for is perhaps better known from the recent work of Richard Dawkins, who named the self-replicating unit of cultural evolution the "meme" in his 1976 book The Selfish Gene.

The idea of BVSR is widely used in cybernetics. For example, the "general problem solver" programs of Allan Newell and Herbert Simon involve two stages, first the blind generation of theorems and then testing of the theorems for validity.

There is some reason to see three parts, and not just two, in BVSR. Campbell clearly distinguishes retention from selection in his writings. In biological evolution, a new characteristic is preserved by inheritance across the generations, whereas natural selection works by differential rates of reproductive success across those generations.

He says that the general model underlying both trial-and-error problem solving and evolution by natural selection has three requirements: "a mechanism for introducing variation, a consistent selection process, and a mechanism for preserving and reproducing the selected variations."

This somewhat resembles Charles Sanders Peirce's famous triad of abduction-induction-deduction, and the three step view of evolution in his unpublished A Guess at the Riddle - "first, the principle of individual variation or sporting; second, the principle of hereditary transmission, which wars against the first principle; and third, the principle of the elimination of unfavorable characters."

Whereas Peirce insisted on absolute chance for his first principle (he called it "tychism" after the Greek for chance, τυχή). Campbell is diffident about real chance. Some systematic or algorithmic variations may be good enough. In this respect, Campbell resembles Daniel Dennett, who believes that deterministic pseudo-randomness is good enough for human free will, and Herbert Simon, whose "generate-and-test" programs usually systematically generate their variations.

Campbell thus prefers the term "blind" to the usual random or chance variations.

a comment on the use of the word "blind" rather than the more usual "random"... Equiprobability is not needed, and is definitely lacking in the mutations which lay the variation base for organic evolution. Statistical independence between one variation and the next, while frequently desirable, can also be spared: in particular, for the generalizations essayed here, certain processes involving systematic sweep scanning are recognized as blind, insofar as variations are produced without prior knowledge of which ones, if any, will furnish a selectworthy encounter. An essential connotation of "blind" is that the variations emitted be independent of the environmental conditions of the occasion of their occurrence.

Popper, in his 1977 lecture at Darwin College entitled Natural Selection and the Emergence of Mind, said he had changed his mind (a rare admission by a philosopher) about two things. First he now thought that natural selection was not a "tautology" that made it an unfalsifiable theory. Second, he had come to accept the random variation and selection of ideas as a model of free will.

The selection of a kind of behavior out of a randomly offered repertoire may be an act of choice, even an act of free will. I am an indeterminist; and in discussing indeterminism I have often regretfully pointed out that quantum indeterminacy does not seem to help us; for the amplification of something like, say, radioactive disintegration processes would not lead to human action or even animal action, but only to random movements.

Popper's model is now the leading two-stage model of free will.

I have changed my mind on this issue. A choice process may be a selection process, and the selection may be from some repertoire of random events, without being random in its turn. This seems to me to offer a promising solution to one of our most vexing problems, and one by downward causation.

Evolutionary epistemology makes all biological functions and all knowledge contingent. But, as Popper says, randomness in the variation stage does not imply random selections.

"Popper's contribution to evolutionary epistemology is to recognize the process of the succession of theories in science as similar selective elimination processes," says Campbell, but this makes their certainty merely probability. "In this perspective," Campbell continues, "Hume's achievement in showing that the best of scientific laws have neither analytic truth nor any other kind of absolute truth seems quite reasonable and appropriate."

Just as Hume denied the power of induction to prove theories, e.g., causality is not proven by any number of similar instances of B following A, Popper denies that induction from a series of observations is the source of a scientific theory. Theories are inventions, hypotheses, conjectures, to be put forward for trial and to be eliminated (refuted) if they conflict with observations. In this Popper follows Peirce's first principle of "abduction" (hypothesis). Campbell says,

In the process, Popper has effectively rejected the model of passive induction even for animal learning, and advocated that here too the typical process involves broad generalizations from single specific initial experiences, generalizations which subsequent experiences edit. It is noteworthy that the best of modern mathematical learning theories posit just such a one-trial learning process, as opposed to older theories which implied inductive accumulation of evidence on all possible stimulus contingencies.

Most noteworthy, Popper is unusual among modern epistemologists in taking Hume's criticism of induction seriously, as more than an embarrassment, tautology, or a definitional technicality. It is the logic of variation and selective elimination which has made him able to accept Hume's contribution to analysis (while rejecting Hume's contribution to the psychology of learning and inference) and to go on to describe that sense in which animal and scientific knowledge is yet possible...

Another older and also more current statement of the epistemological problem is also eschewed. This is the identification of "knowledge" not as "true belief" but as "true belief" which is also "rationally justified" or "well-grounded." Though widely used in linguistic analysis, this point of view implicitly accepts as valid an inductivist epistemology (giving but superficial lip service to Hume in recognizing such induction as providing only approximate validity). Popper does not limit truth to those statements which have rational support or are well-grounded before they are asserted. Truth rather lies in the outcome of subsequent tests.

James departs from the more complete model presented in Poincaré, Mach, and Campbell by seemingly having the full range of mental variations selected by the external environment rather than recognizing the existence of mental selectors, which vicariously represent the external environment (the selected products, of course, being subject to further validation in overt locomotion, etc.)
(Evolutionary Epistemology, p. 65)

And I can easily show...that as a matter of fact the new conceptions, emotions, and active tendencies which evolve are originally produced in the shape of random images, fancies, accidental out-births of spontaneous variation in the functional activity of the excessively instable human brain, which the outer environment simply confirms or refutes, adopts or rejects, preserves or destroys, - selects, in short, just as it selects morphological and social variations due to molecular accidents of an analogous sort.

James does not literally mean here that the environment selects, but only in the Kantian sense that we put our questions to Nature and nature responds.

In his following paragraphs, James beautifully describes the origin of new ideas as "the most abrupt cross-cuts and transitions from one idea to another, the most rarefied abstractions and discriminations, the most unheard-of combinations of elements, the subtlest associations of analogy; in a word, we seem suddenly introduced into a seething caldron of ideas, where everything is fizzling and bobbing about in a state of bewildering activity."

He says that "their genesis is sudden and, as it were, spontaneous. That is to say, the same premises would not, in the mind of another individual, have engendered just that conclusion." That the conclusion is the product of a mind choosing from alternative possibilities, James affirms as "the steadfastness of a human will capable of alternative choice."

The basic idea of downward causal control had been put forward some years earlier by Roger Sperry in his 1965 lecture to the Humanist Association in Chicago and his 1969 article in Psychological Review.

Sperry cited a wheel rolling downhill as an example of downward causal control. The atoms and molecules are caught up and overpowered by the higher properties of the whole. He compares the rolling wheel to an ongoing brain process or a progressing train of thought in which the overall properties of the brain process, as a coherent organizational entity, determine the timing and spacing of the firing patterns within its neural infrastructure.

In 1977, Karl Popper changed his mind on the importance of indeterminism. He developed a two-stage model of free will and said that it was an example of downward causation!

Popper cited both Sperry and Campbell as the source of the idea of downward causation.