If the resident zoologist of Galaxy X had visited the earth 5 million years ago while making his inventory of inhabited planets in the universe, he would surely have corrected his earlier report that apes showed more promise than Old World monkeys and noted that monkeys had overcome an original disadvantage to gain domination among primates. (He will confirm this statement after his visit next year–but also add a footnote that one species from the ape bush has enjoyed an unusual and unexpected flowering, thus demanding closer monitoring.)

In order that an inventory of plants may be begun and a classification of them correctly established, we must try to discover criteria of some sort for distinguishing what are called “species”. After a long and considerable investigation, no surer criterion for determining species had occurred to me than distinguishing features that perpetuate themselves in propagation from seed. Thus, no matter what variations occur in the individuals or the species, if they spring from the seed of one and the same plant, they are accidental variations and not such as to distinguish a species. For these variations do not perpetuate themselves in subsequent seeding. Thus, for example, we do not regard caryophylli with full or multiple blossoms as a species distinct from caryophylli with single blossoms, because the former owe their origin to the seed of the latter and if the former are sown from their own seed, they once more produce single-blossom caryophylli. But variations that never have as their source seed from one and the same species may finally be regarded as distinct species. Or, if you make a comparison between any two plants, plants which never spring from each other's seed and never, when their seed is sown, are transmuted one into the other, these plants finally are distinct species. For it is just as in animals: a difference in sex is not enough to prove a difference of species, because each sex is derived from the same seed as far as species is concerned and not infrequently from the same parents; no matter how many and how striking may be the accidental differences between them; no other proof that bull and cow, man and woman belong to the same species is required than the fact that both very frequently spring from the same parents or the same mother. Likewise in the case of plants, there is no surer index of identity of species than that of origin from the seed of one and the same plant, whether it is a matter of individuals or species. For animals that differ in species preserve their distinct species permanently; one species never springs from the seed of another nor vice versa.

The knowledge we have aquired ought not to resemble a great shop without order, and without inventory; we ought to know what we possess, and be able to make it serve us in our need.

The scientific method is a potentiation of common sense, exercised with a specially firm determination not to persist in error if any exertion of hand or mind can deliver us from it. Like other exploratory processes, it can be resolved into a dialogue between fact and fancy, the actual and the possible; between what could be true and what is in fact the case. The purpose of scientific enquiry is not to compile an inventory of factual information, nor to build up a totalitarian world picture of Natural Laws in which every event that is not compulsory is forbidden. We should think of it rather as a logically articulated structure of justifiable beliefs about nature. It begins as a story about a Possible World—a story which we invent and criticise and modify as we go along, so that it ends by being, as nearly as we can make it, a story about real life.

The unscientific person takes things as they are, and cares not for their origin. To study things from a scientific standpoint means to take an inventory of them—to find the process in which they are being produced; to connect them with other things; to see things in their causal process.

There are three stages in the development of science: First, there is the observation of things and facts—the scientists map out and inventory the objects in each department of Nature; secondly, the interrelations are investigated, and this leads to a knowledge of forces and influences which produce or modify those objects…. This is the dynamic stage, the discovery of forces and laws connecting each fact with all other facts, and each province of Nature with all other provinces of Nature. The goal of this second stage of science is to make each fact in Nature throw light on all the other facts, and thus to illuminate each by all. … Science in its third and final stage learns to know everything in Nature as a part of a process which it studies in the history of its development. When it comes to see each thing in the perspective of its evolution, it knows it and comprehends it.

When a conjecture inspires new hopes or creates new fears, action is indicated. There is an important asymmetry between hope, which leads to actions that will test its basis, and fear, which leads to restriction of options frequently restricting testing of the basis for the fear. As we know only too well, many of our hopes do not survive their tests. However, fears accumulate untested. Our inventory of untested fears has always made humanity disastrously vulnerable to thought control. While science was independent of politics, its greatest triumph was the reduction of that vulnerability.