It is wrong for a man to say that he is certain of the objective truth of any proposition unless he can produce evidence which logically justifies that certainty.
It is an error to imagine that evolution signifies a constant tendency to increased perfection. That process undoubtedly involves a constant remodeling of the organism in adaptation to new conditions; but it depends on the nature of those conditions whether the direction of the modifications effected shall be upward or downward.
Interpretation
What this quote means
Evolution does not always lead to improvement; it depends on environmental conditions.
In this quote, Thomas Huxley emphasizes that evolution is not a linear process aiming for perfection. Instead, the adaptations an organism makes in response to changing conditions can lead to various outcomes, which may be beneficial in some scenarios and detrimental in others. Huxley highlights that the nature of the conditions an organism faces ultimately determines the trajectory of its evolutionary changes, challenging the common misconception of evolution as a march towards perfection.
Themes
In practice
Example use cases
This quote can be used in a lecture on evolution to illustrate misconceptions about the process.
More from Thomas Huxley
All quotes βThe child who has been taught to make an accurate elevation, plan, and section of a pint pot has had an admirable training in accuracy of eye and hand.
Let us have "sweet girl graduates" by all means. They will be none the less sweet for a little wisdom; and the "golden hair" will not curl less gracefully outside the head by reason of there being brains within.
The secret of genius is to carry the spirit of childhood into maturity.
It is the first duty of a hypothesis to be intelligible.
Of the few innocent pleasures left to men past middle life, the jamming of common sense down the throats of fools is perhaps the keenest.
Similar quotes
After I give lectures-on almost any subject-I am often asked, "Do you believe in UFOs?" I'm always struck by how the question is phrased, the suggestion that this is a matter of belief and not evidence. I'm almost never asked, "How good is the evidence that UFOs are alien spaceships?"
If you want to find out anything from the theoretical physicists about the methods they use, I advise you to stick closely to one principle: don't listen to their words, fix your attention on their deeds. To him who is a discoverer in this field the products of his imagination appear so necessary and natural that he regards them, and would like to have them regarded by others, not as creations of thought but as given realities.
The most important discoveries will provide answers to questions that we do not yet know how to ask and will concern objects we have not yet imagined.
The role of radiologists will evolve from doing perceptual things that could probably be done by a highly trained pigeon to doing far more cognitive things.
No isolated experiment, however significant in itself, can suffice for the experimental demonstration of any natural phenomenon; for the "one chance in a million" will undoubtedly occur, with no less and no more than its appropriate frequency, however surprised we may be that it should occur to us.
I belonged to a small minority of boys who were lacking in physical strength and athletic prowess. ... We found our refuge in science. ... We learned that science is a revenge of victims against oppressors, that science is a territory of freedom and friendship in the midst of tyranny and hatred.