Evolutionism and Logic
Dominique Tassot

Abstract: Since evolutionism rests upon premises and inductive and deductive arguments, it may be useful to test them against the principles of logic. In relation to the principle of non-contradiction, one finds numerous contradictory affirmations (continuity and discontinuity, gradualism and saltationism, and, above all, extrapolation from observation to the contrary of what has been observed). In relation to the identity principle, one notes shifts of meaning (as between macro and microevolution). Many authors have mentioned the frequent use of circulus vitiosus; to this will be added here the refusal to make a decision, to follow the thought process to its natural end by affirming as true or at least most probable the contrary of what has been shown to be false. Finally, several premises have proven to be factually questionable, such as the progressive nature of evolution or the attribution to time of a causative power. So many logical anomalies call into question the scientific status of the evolutionary hypothesis.

One of the purposes of this paper is to demonstrate that evolution lacks the necessary precision to qualify as a scientific hypothesis. In the absence of a universally-accepted, precise definition, one may define the evolutionary hypothesis as the thesis that all living organisms derive from each other and initially arose from non-living matter, all of this happening through natural processes over long periods of geological time. Evolutionism may be defined as faith in the truth of this hypothesis as if it had already been demonstrated.

Contra factum non est argumentum. The existence of a debate about evolution in the very bosom of the scientific community constitutes an indirect proof that the "fact" of evolution has never been established. Due to the lack of direct evidence, evolution takes hold of our mindsand this happened with Lamarck and Darwin as well as with their successorsunder the cover of arguments, illustrations and interpretations.

Consequently, logic has something to say about evolutionism; especially since its affirmation of a progressive development of living beings is disconcerting to common sense. Indeed, this claim runs contrary to ones every day experience of the re-production of species, and it constantly invokes long ages so vast that imagination alone can encompass them.

1. Contradictions

The most evident breach of the rules of logic is contradiction: the fact of affirming at the same time something and its contrary. This is flagrantly observed in four common theses of evolutionist speech.

1.1. Contradiction between causes and effects

According to the “actualist” postulate that provided the foundation for the geological framework within which a progressive evolution of living beings could be traced over the course of time, the present is the key of the past. For James Hutton (1728-1797), one of the chief proponents of this formula, the stone that falls today cannot have lifted itself yesterday. Therefore, it is up to “actual” causes alone — that is to say real causes that can still be observed — to explain the formation of landscapes and the appearance of living beings. But these actual causes, which we see in our every-day lives, only alter landscapes, and do not shape them. And the living beings that we observe "re-produce" themselves, letting only slight modifications appear from one generation to the next. The general rule, without which no science is possible, consists in asserting that the same causes always produce the same effects.

In this way it is possible to reason from observed effects to their corresponding causes. But evolutionism affirms that these same causes, able to produce today small variations inside species, long ago produced effects of a different nature or on a very different scale, such as the transformation of reptiles into birds or of land mammals into whales. Here lies a first contradiction, sufficient by itself to show that evolutionism is not a sound scientific thesis.

1.2. Continuity and numerical discontinuity between beings.

Classification of living beings proceeds through dichotomies. One distinguishes, for each feature, those groups of organisms that have it and those that do not. For instance, plants may be divided according to the number of "cotyledons" present in the seed for feeding the young shoot: one or two. We have monocotyledons and dicotyledons, thus showing a discontinuity among plants. However, evolutionism affirms a universal continuity.

Now, functional organs are necessarily built according to whole numbers, and no intermediary may exist between two succeeding whole numbers: a young shoot cannot put forth a decimal fraction of a leaf or root; an animal cannot have a fractional number of legs.

Lamarck's giraffe, whose neck extended by dint of stretching for tree-leaves, remains credible as long as one sees in it only flesh and skin. But, between the zebra and the giraffe, there is not only a difference in the length of the neck; there is also a difference in the number of vertebrae. The same cause that would be able to continuously transform the muscles of an organism would not be able to add even a single vertebra. Therefore, it is impossible to affirm continuity between living beings, while admitting at the same time the evident discontinuities concerning the number of their organs.

1.3. Gradualism and saltationism

Darwin's fundamental thesis consists in a gradual evolution, through small imperceptible modifications, whose accumulation would bring, at length, clear morphological differences. However, the fossil record does not show a single intermediary being: differences between fossils are as marked as between organisms living today, so that the same general taxonomical classification can be used to describe them. Some palaeontologists have tried to resolve the difficulty by affirming an evolution by jumps: long stable periods interrupted by short transitions of rapid evolution, which would thus be unable to produce numerous fossils. But it is impossible to maintain gradualism (which gives a credible mechanism for evolution) while using saltationism to explain the absence of “transitional” fossils.

1.4. Extrapolation of the contrary

Extrapolation is an accepted practice in science, whereby an assertion is extended beyond the framework within which an observation has been made. One can easily admit that a regularity noticed for a sufficiently long time will continue to manifest itself. Prediction of a solar eclipse (extrapolation towards the future) or of a voting poll (extrapolation from a limited sample to the whole population) constitute extrapolations. But an extrapolation makes sense only when what is affirmed is identical to what has been observed.

Now, observations of living beings testify to the permanency of species: variability (which is considerable) remains always within specified limits. Thus, innumerable mutations produced over decades on the fruit fly or on colon bacillus have never produced anything other than fruit flies or colon bacillus. In this case, the rule requires that what should be extrapolated is the stability of the species as such. But evolutionist reasoning consists in saying that, given enough time, the very contrary will happen.

These few examples should be sufficient to remove the evolutionary hypothesis from the field of natural science and to place it definitively in the realm of literary fiction. But many other logical anomalies remain to be exposed.

2 The shifts of meaning

A common rule in all sciences consists in giving a precise definition of all the words in use, and sticking to it. On the contrary, evolutionist speech creates confusion by using words susceptible of several interpretations or by using words out of their true context. In this way it is possible, almost without noticing it, to modify the extension or the comprehension of the terms in use.

2.1. Homo: species or kind?

A typical example concerns the term Homo. The common taxonomic rule names the species with a substantive and uses an adjective to modify the substantive with varieties or subspecies.

In this manner, Canis lupus, Wolf, is distinguished from Canis canis, Dog. Homo refers to a species: all human races interbreed and, even if this criterion is somewhat difficult to use in palaeontology, it seems that Homo sapiens and Homo neanderthalensis have produced crossbreeds in the past. Surprisingly, Homo habilis or Homo erectus are called Homo, although they are clearly distinct from Homo sapiens, making here of Homo at least a kind, grouping together different species somehow morphologically close, as concerns their skeletons, but lacking a genetic link—even if evolutionists postulate a common ancestor (never found in practice).

2.2. Macro and micro-evolution

Living species demonstrate a considerable variability (Agassiz, a great adversary of Darwin, used the word “pliability”). It remains, however, limited to secondary features such as colour, fur thickness, height, shape of the beak, and so on, and this “microevolution” distinguishes itself clearly from a trans-specific transformation that would apply to the structure or function of organs.

The change from scales to feathers or from fins to legs concerns “macroevolution”. Thus, the same term “evolution” is being used to designate two categories of phenomena without any common link: innumerable observed facts confirm the reality of microevolution, whereas macroevolution lacks any kind of empirical evidence or theoretical basis.1 But the inescapable confusion between two concepts designated with the same word credits the idea of macroevolution with all the proofs of a well attested microevolution.

2.3. “Natural” selection

Darwin's book insidiously entitled On the Origin of Species by Means of Natural Selection (in it are minutely described intra-specific variations, never the origin, i.e. the appearance of a new species) is based upon the idea that Nature imitates breeders who modify the features of a race by a careful choice of their breeding stock. But such a “selection” is an intelligent act, set by a conscious subject towards a definite aim. However, Darwin makes use of the same word, "selection" to designate a blind act of Nature, thus giving chance the credit for an effect which implies a purpose.

2.4. Evolutionary adaptation

Adaptive phenomena are well known, including adaptive mutations. But it is paradoxical to extend the meaning of the word "adaptation" to indicate the appearance of new bodily organs. As well known evolutionist biologist Richard Lewontin2 remarks, it is contradictory to describe evolution as a process of adaptation—since all living beings are already adapted.

Natural selection may influence only pre-existing organs: therefore, if wings or eyes came before natural selection, the latter is unable to explain their origin.

3. Circular reasoning

When one concludes by the very premise that has been supposed in the beginning, nothing has been demonstrated. Such a paralogism, circulus vitiosus, is so omnipresent in evolutionist thinking, that it remains unconscious most of the time: the grid used for reading the facts, ends up not being perceived any longer as a hypothetical construct and thus forms one body with the observations.

3.1. Survival of the fittest

It is a simple tautology, and admitted as such by many evolutionists themselves. As a matter of fact, fitness is defined by the capacity to survive. That is to say, the fittest is, ipso facto, the one who survived, so that nothing new has been demonstrated by affirming that it is the fittest who survive.

3.2. Stratigraphic scale

According to the stratigraphic scale, geological layers are classified by attributing to each period or each level "index fossils." Supposing that the genealogical tree of marine living beings has been duly established, selected fossils relatively frequent and peculiar to each geological "facies" are identified; then a relative age can be given to each fossil. As these “index fossils” have been previously ordered according to their appearance on the "tree" of life, it is unmistakably observed in the field that the age of rocks confirms evolution theory: the "more ancient" fossil will be found in the older rock, and the "older" rock will contain the fossils of the more ancient organisms.

3.3. The burden of the proof

Within each of the natural sciences, facts are described and interpreted within the evolutionist paradigm, which is accepted as true. As regards the proof of the evolutionary hypothesis, it is assumed that it will be provided by the other disciplines involved, so that it is not necessary for a scientist to be concerned with it. For palaeontologists, the proof can be found in biology; for biologists, in geology; and for geologists, in palaeontology. In such a way, as already noted by Béchamp, the first Dean of Lille Catholic University, more than a century ago, about evolutionism: “we suppose, and suppose again, and after supposition upon supposition, we end by concluding without proof."3

4. The refusal to make a decision

According to the very fruitful rules inherited from Greek thought, the contradictory of a false proposition is true, and reciprocally (principle of contradiction). But evolutionists, constrained by the iron rule of their paradigm, brush aside the application of this principle and condemn themselves to allow contradictory positions to co-exist within their thinking.

4.1. Gradualism

Palaeontology establishes the absence of gradualism between the different forms of life, and this assertion is now considered as definitely proven. The hunt for "missing links" has stopped (except in the field of human palaeontology).

Gradualism would imply continuity between the forms of life: morphological, physiological and genetic continuity. The contrary of gradualism is discontinuity. Thus, negation of gradualism leads to the affirmation of a discontinuity between the forms of life, then to the negation of a hereditary link: dissimilarity strongly suggests non-descent.

This affirmation is nevertheless dismissed and evolutionist speech invokes “jumps” —a purely verbal solution—as such “jumps” are just beings of reason, devoid of any other justification but to circumvent the principle of contradiction.

4.2. Mutationism

Resorting to mutations is the artificial means by which, at the beginning of the 20th century, a radical objection was circumvented—one which applied just as well to Lamarckism as to Darwinism—the discovery of the non-heredity of acquired characteristics: job skills, for instance, are not transmitted to descendants. On the contrary, mutations, as they operate at the genome level, consist in novelties transmissible to descendants. Now a century has passed since the first publication on mutations by Hugo de Vries (1910), and observation as well as experimentation both confirm that mutations never overstep the barrier of the species (the case of speciation being irrelevant here, as no new organs appear). From this failure the contrary affirmation should follow: mutations confirm the permanence of the species as such, with its internal variability. But evolutionists reject this affirmation.

4.3. Finalism

The refusal to recognize a purpose clearly visible in all living beings is considered by Nobel Prize-winning biologist Jacques Monod, as "the corner stone of the scientific method."4 Then, this spokesman of an “objective” biology adds: "Objectivity, however, obliges us to admit the teleonomical character of living beings, to admit that, in their structure and performances, they indeed realize and pursue a goal. Here lies, at least apparently, a profound epistemological contradiction."5

For it is impossible to exclude any kind of purpose from nature. The constitution and arrangement of bodily organs constitute a tangible proof of that.

Confronted with this kind of evidence, instead of reaffirming the validity of teleology, as did all the founders of taxonomy, from Aristotle and Galen to Ray and Linnaeus, evolutionists have resorted to linguistic contortions. They would speak of “entelechy” (Naegeli), of “non-mechanical cause” (Driesch), of “anti-chance” (Simpson), of “teleological determinism” (Cuénot), of “teleonomy” (Monod), of a “logic” in living being (Jacob), etc. However, true logic would rather insist that the intelligibility of living beings demands that we take into account the obvious existence of purpose in nature.

These verbal evasions are only ways to escape the consequences of a refusal to make a decision when faced with a contradiction. Then one will inevitably think of the criterion suggested by Popper: a scientific a theory is one that can be “falsified”, that could be proven false. As soon as evolutionists believe that they can answer objections with a simple shift of vocabulary, they expose, ipso facto, the non-scientific nature of the thesis they promote.

5. False premises

According to Fénelon, “Most errors men make do not result from the fact that they reason wrongly on the basis of true principles, but from the fact that they reason rightly on the basis of false principles or of inexact considerations.

Evolutionism also fits within this framework. Let us mention some of these false premises.

5.1. Evanescence of species

Lamarck as well as Darwin took a nominalist view of species, admitting the real existence only of individual beings. In a letter to Asa Gray, Darwin despaired of winning over "naturalists, who persist in believing that species are entities."6 Two centuries after the publication of the Philosophie zoologique by Lamarck, we cannot fail to observe that the concept of species is both functional and indispensable to science, and that the criterion chosen as the most pertinent marker of membership in a species, even by a Darwinian biologist like Edwin Mayr, remains interbreeding: a genuine and objective criterion, which is in no way purely formal or arbitrary.

One might add that, as Grassé observed—and he occupied the chair of Evolution at Paris-Sorbonne University—numerous experiments using mutations have been performed for decades on the fruit fly to prove evolution but instead merely confirmed the real existence and dynamic stability of living species.

5.2. Progressive Evolution

Evolution is always described as a progressive process which improves living beings. As a matter or fact, the exact contrary is observed: mutations are either regressive or neutral (from the point of view of the species), and the formation of sub-species or races is always a form of specialization which impoverishes the gene pool and limits the intermixing of genes.

5.3. Time as a cause

Lamarck used to justify “transformism” through two causes: time and favourable circumstances, "of which Nature has no lack."7

If time is used to measure natural transformations, time is not their author nor agent, however many millions of years are available. George Wald, in The Origin of Life, writes this surprising phrase in a science book: "The duration we have to consider here is in a range of two billion years; therefore it would be meaningless to judge something impossible on the basis of human experience. In so long a time, the impossible becomes possible, the possible probable, and the probable virtually certain. We just need to wait: time will alone accomplish the miracle."8 Any logical comment here would be superfluous.

5.4. "Genealogical" trees

Numerous books and journals present “genealogical trees” concerning such and such a taxonomical category, and even sometimes a “tree of life” including all living forms.

A tree is composed of trunk, branches and leaves.

In the present case, only leaves really exist, consisting in living and fossil species. The rest of the tree is nothing but an artificial construct, as “common ancestors” reside only in the naturalists' imagination. The large and smaller branches are presented as having evolved according to the appearance of the increasingly specialised categories of taxonomy, becoming more specialized with the passage of time: classes, orders, families, genera, and at last species. But each taxon shows well determined characteristics. Thus, mammals possess mammalian glands, sudoriferous glands, a hair system, a heart with four chambers and an aorta on the left side, a diaphragm, three ossicles in the ear, etc. These features remain when one goes downwards to the families and genera: indeed, “descendants” reproduce all of the characteristics of their “ancestors” and add their own.

Therefore, it is contradictory to the "tree of life" to consider that a Fish or a Reptile (whose lungs, skin, ears, etc., are organized differently) may have been the ancestor of Mammals. It is impossible for the branches of the taxonomic tree, to represent functional living beings. The "tree of life" does not exist.


It is necessary to clearly distinguish the facts of life (the living beings, their organs and functions, their metabolism, their reproduction, etc.) and the interpretation of these same facts. The evolutionary hypothesis imposes upon the facts a general paradigm, and the latter pretends to explain everything, as it gives an account of the origin—and therefore the truth—of all living beings. If this were really the case, the theory would be predictive and the rules of logic would apply to evolutionary biology as well as they do in any other field of science.

Now if the intellectual products of evolutionism show so many logical anomalies, it becomes legitimate to question not only such and such a premise or paralogism, but the legitimacy of the paradigm itself.

1 E. SZATHMARY and J.MAYNARD SMITH, "The Major Evolutionary Transitions", Nature 374, pp 227-232: "There is no theoretical basis for believing that evolutionary lines become more complex with time; and there is also no empirical evidence that this happens."
2 RICHARD LEWONTIN, "Adaptation", Scientific American, vol. 239, n° 3 (1978), September, p.159.
3 ANTOINE BÉCHAMP, Sur l’état présent des rapports de la Science et de la Religion au sujet de l’origine des êtres organisés, Quarré, Lille (1877), p.9.
4 JACQUES MONOD, Le Hasard et la Nécessité, Le Seuil, Paris (1970), p.37.
5 Ibid., p.38.
6 DARWIN, La vie et la correspondance de Charles Darwin, avec un chapitre autobiographique, publiés par son fils M. Francis Darwin (1887), French Trans. by Henry de Varigny, Reinwald, Paris (1888), vol. II, p. 83.
7 LAMARCK,"Discours d'Ouverture (An VIII, An X,An XI et 1806)", in Bulletin scientifique de la France et de la Belgique, vol. XI, Paris (1907), p.27.
8 See G. SERMONTI and R. FONDI, Dopo Darwin, Rusconi, Milan (1980), p.177.