Long before the reader has arrived at this part of my work, a crowd of difficulties will have occurred to him. Some of them are so serious that to this day I can hardly reflect on them without being in some degree staggered

Charles Darwin

Darwin’s Own Doubts About His Theory

Often a cold shudder has run through me, and I have asked myself whether I may have not devoted myself to a fantasy

Letter to Geologist Charles Lyell, November 23, 1859

“…I am quite conscious that my speculations run beyond the bounds of
true science….It is a mere rag of an hypothesis with as many flaw[s] &
holes as sound parts.” Charles Darwin to Asa Gray

Cited by Adrian Desmond and James Moore, Darwin, (New York: W.W. Norton and
Company, 1991) pp. 456, 475.

To the question why we do not find records of these vast primordial periods, I can give no satisfactory answer.”

“The case at present must remain inexplicable; and may be truly urged as a valid argument against the views here entertained.”

On The Origin Of Species: Page 308

Nevertheless you have expressed my inward conviction, though far more vividly and clearly than I could have done, that the Universe is not the result of chance. But then with me the horrid doubt always arises whether the convictions of man’s mind, which has been developed from the mind of lower animals, are of any value or at all trustworthy. Would any one trust in the convictions of a monkey’s mind , if there are any convictions of such a mind?

Charles Darwin: Letter to William Graham July 3, 1881

Darwin On The Fossil Record And The Absence Of Transitional Forms

I do not pretend that I should ever have suspected how poor a record of the mutations of life, the best preserved geological section presented

On The Origin Of Species: fourth British edition (1866), page 364

“When we descend to details, we can prove that no one species has changed [i.e., they cannot prove that a single species has changed]; nor can we prove that the supposed changes are beneficial, which is the groundwork of the theory. Nor can we explain why some species have changed and others have not”

Letter to colleagues Darwin 1899, 2:210

By this my theory innumerable transitional forms must have existed, why do we not find them embedded in countless numbers in the crust of the earth? …But it may be urged that when several closely allied species inhabit the same territory, we surely ought to find at the present time many transitional forms. Let us take a simple case: in travelling from north to south over a continent, we generally meet at successive intervals with closely allied or representative species, evidently filling nearly the same place in the natural economy of the land. These representative species often meet and interlock; and as the one becomes rarer and rarer, the other becomes more and more frequent, till the one replaces the other. But if we compare these species where they intermingle, they are generally as absolutely distinct from each other in every detail of structure as are specimens taken from the metropolis inhabited by each. By my theory these allied species are descended from a common parent; and during the process of modification, each has become adapted to the conditions of life of its own region, and has supplanted and exterminated its original parent-form and all the transitional varieties between its past and present states. Hence we ought not to expect at the present time to meet with numerous transitional varieties in each region, though they must have existed there, and may be embedded there in a fossil condition. But in the intermediate region, having intermediate conditions of life, why do we not now find closely-linking intermediate varieties? This difficulty for a long time quite confounded me.

On The Origin Of Species, Chapter 6 Difficulties Of The Theory

Why, if species have descended from other species by fine gradations, do we not everywhere see innumerable transitional forms? Why is not all nature in confusion, instead of the species being, as we see them, well defined?

On The Origin Of The Species-Chapter 6 Difficulties Of The Theory

The abrupt manner in which whole groups of species suddenly appear in certain formations, has been urged by several palaeontologists as a fatal objection to the belief in the transmutation of species. If numerous species, belong to the same genera or families, have really started into life all at once, the fact would be fatal to the theory of descent with slow modification through natural selection.

On The Origin Of Species:fourth British edition (1866), page 364

“Consequently, if my theory be true, it is indisputable that before the lowest Silurian stratum was deposited, long periods elapsed, as long as, or probably far longer than, the whole interval from the Silurian age to the present day; and that during these vast, yet quite unknown, periods of time, the world swarmed with living creatures. To the question why we do not find records of these vast primordial periods, I can give no satisfactory answer.”

I concluded that this great group had been suddenly developed at the commencement of the tertiary series This was a sore trouble to me, adding as I thought one more instance of the abrupt appearance of a great group of species. ”

“The case most frequently insisted on by paleontologists of the apparently sudden appearance of a whole group of species, is that of the teleostean fishes, low down in the Chalk period.”

Origin Of Species p. 284

“On the sudden appearance of groups of Allied Species in the lowest known fossilferous strata: There is another and allied difficulty, which is much graver. I allude to the manner in which numbers of species of the same group suddenly appear in the lowest known fossiliferous rocks.

Origin Of Species

“Consequently, if my theory be true, it is indisputable that before the lowest Silurian stratum was deposited, long periods elapsed, as long as, or probably far longer than, the whole interval from the Silurian age to the present day; and that during these vast, yet quite unknown, periods of time, the world swarmed with living creatures. To the question why we do not find records of these vast primordial periods, I can give no satisfactory answer.

Origin Of Species p. 286

“The case at present must remain inexplicable; and may be truly urged as a valid argument against the views here entertained.”

Origin Of Species Chapter 10 p 334

“The several difficulties here discussed, namely our not finding in the successive formations infinitely numerous transitional links between the many species which now exist or have existed; the sudden manner in which whole groups of species appear in our European formations; the almost entire absence, as at present known, of fossiliferous formations beneath the Silurian strata, are all undoubtedly of the gravest nature.”

Origin Of Species Chapter 9

Darwin On Genetics And Common Ancestry

How can we account for species, when crossed, being sterile and producing sterile offspring, whereas, when varieties are crossed, their fertility is unimpaired?

On The Origin Of The Species-Chapter 6 Difficulties Of The Theory

It has been asked by the opponents of such views as I hold, how, for instance, could a land carnivorous animal have been converted into one with aquatic habits; for how could the animal in its transitional state have subsisted?

Here, as on other occasions, I lie under a heavy disadvantage, for, out of the many striking cases which I have collected, I can give only one or two instances of transitional habits and structures in allied species; and of diversified habits, either constant or occasional, in the same species. And it seems to me that nothing less than a long list of such cases is sufficient to lessen the difficulty in any particular case like that of the bat.

On The Origin Of The Species-Chapter 6 Difficulties Of The Theory

“But then with me the horrid doubt always arises whether the convictions of man’s mind, which has been developed from the mind of the lower animals, are of any value or at all trustworthy. Would any one trust in the convictions of a monkey’s mind, if there are any convictions in such a mind?

Charles Darwin, Letter to William Graham July 3, 1881

The subject of instinct might have been worked into the previous chapters; but I have thought that it would be more convenient to treat the subject separately, especially as so wonderful an instinct as that of the hive-bee making its cells will probably have occurred to many readers, as a difficulty sufficient to overthrow my whole theory. I must premise, that I have nothing to do with the origin of the primary mental powers, any more than I have with that of life itself.

On The Origin Of The Species Chapter 7

This hypothesis [common descent ] must be tested … by trying to see whether it explains several large and independent classes of facts; such as the geological succession of organic beings, and their distribution in past and present times, and their mutual affinities and homologies.

Charles Darwin, Stephen Meyer: Creation Hypothesis

Darwin On Intelligent Design And Complexity

Charles Darwin Letter To ND. Doedes April 2, 1873

Is it possible that an animal having, for instance, the structure and habits of a bat, could have been formed by the modification of some other animal with widely different habits and structure? Can we believe that natural selection could produce, on the one hand, an organ of trifling importance, such as the tail of a giraffe, which serves as a fly-flapper, and, on the other hand, an organ so wonderful as the eye?

On The Origin Of Species-Chapter 6 Difficulties Of The Theory

Can instincts be acquired and modified through natural selection? What shall we say to the instinct which leads the bee to make cells, and which has practically anticipated the discoveries of profound mathematicians?

On The Origin Of The Species-Chapter 6 Difficulties Of The Theory

To suppose that the eye with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest degree.

On The Origin Of Species-Chapter 6 Difficulties Of The Theory

As natural selection acts by life and death, by the survival of the fittest, and by the destruction of the less well-fitted individuals, I have sometimes felt great difficulty in understanding the origin or formation of parts of little importance; almost as great, though of a very different kind, as in the case of the most perfect and complex organs.

In the first place, we are much too ignorant in regard to the whole economy of any one organic being to say what slight modifications would be of importance or not. In a former chapter I have given instances of very trifling characters, such as the down on fruit and the colour of its flesh, the colour of the skin and hair of quadrupeds, which, from being correlated with constitutional differences, or from determining the attacks of insects, might assuredly be acted on by natural selection. The tail of the giraffe looks like an artificially constructed fly-flapper; and it seems at first incredible that this could have been adapted for its present purpose by successive slight modifications, each better and better fitted, for so trifling an object as to drive away flies

On The Origin Of Species-Chapter 6 Difficulties Of The Theory

The foregoing remarks lead me to say a few words on the protest lately made by some naturalists against the utilitarian doctrine that every detail of structure has been produced for the good of its possessor. They believe that many structures have been created for the sake of beauty, to delight man or the Creator (but this latter point is beyond the scope of scientific discussion), or for the sake of mere variety, a view already discussed. Such doctrines, if true, would be absolutely fatal to my theory. I fully admit that many structures are now of no direct use to their possessors, and may never have been of any use to their progenitors; but this does not prove that they were formed solely for beauty or variety.

On The Origin Of Species-Chapter 6 Difficulties Of The Theory

Darwin On Mutations And Time

If it could be demonstrated that any complex organ existed which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down.

On The Origin Of Species Chapter 6 Difficulties Of The Theory

Although we must be extremely cautious in concluding that any organ could not have been produced by successive, small, transitional gradations, yet undoubtedly serious cases of difficulty occur.

One of the most serious is that of neuter insects, which are often differently constructed from either the males or fertile females; but this case will be treated of in the next chapter. The electric organs of fishes offer another case of special difficulty; for it is impossible to conceive by what steps these wondrous organs have been produced.

On The Origin Of Species-Chapter 6 Difficulties Of The Theory

If, moreover, they had been the progenitors of these orders, they would almost certainly have been long ago supplanted and exterminated by their numerous and improved descendants.

Consequently, if my theory be true, it is indisputable that before the lowest Silurian stratum was deposited, long periods elapsed, as long as, or probably far longer than, the whole interval from the Silurian age to the present day; and that during these vast, yet quite unknown, periods of time, the world swarmed with living creatures.

To the question why we do not find records of these vast primordial periods, I can give no satisfactory answer.

On The Origin Of Species-Chapter 9 Page 307

Darwin’s Fluctuations On God As Creator

The question of whether there exists a Creator and ruler of the universe has been answered in the affirmative by some of the highest intellects that have ever existed

Charles Darwin: The Descent of Man

Another source of conviction in the existence of God, connected with the reason and not with the feelings, impresses me as having much more weight. This follows from the extreme difficulty or rather impossibility of conceiving this immense and wonderful universe, including man with his capacity of looking far backwards and far into futurity, as the result of blind chance or necessity. When thus reflecting I feel compelled to look to a First Cause having an intelligent mind in some degree analogous to that of man; and I deserve to be called a Theist

Charles Darwin: Autobiography

The impossibility of conceiving that this grand and wondrous universe, with our conscious selves, arose through chance, seems to me the chief argument for the existence of God; but whether this is an argument of real value, I have never been able to decide.

On The Origin Of Species-Chapter 6 Difficulties Of The Theory

 He says he is going to review me in [his] yearly Report. My good and kind agent for the propagation of the Gospel -i.e., the devil’s gospel. Ever Yours, Charles Darwin.

Darwin to T. H. Huxley Aug. 8, 1860

In my most extreme fluctuations I have never been an atheist in the sense of denying the existence of a God.— I think that generally (& more and more so as I grow older) but not always, that an agnostic would be the most correct description of my state of mind.”[1]

Charles Darwin: Letter to John Fordyce, May 7, 1879