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 →The 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
I wouldn't have thought that a wrong theory should lead us to understand better the ordinary quantum field theories or to have new insights about the quantum states of black holes.
People often ask me why I persisted in doing research on a subject that was so controversial. I frequently respond by telling them that only a few scientists are granted the great fortune to pursue topics that are so new and different that only a small number of people can grasp the meaning of such discoveries initially.
The problem with intelligent-design theory, is not that it is false but that it is not falsifiable. Not being susceptible to contradicting evidence, it is not a testable hypothesis. Hence it is not a scientific but a creedal tenet - a matter of faith, unsuited to a public school's science curriculum.
When scientifically investigating the natural world, the only thing worse than a blind believer is a seeing denier.
The overwhelming majority of theories are rejected because they contain bad explanations, not because they fail experimental tests.
I am an enthusiast, but not a crank in the sense that I have some pet theories as to the proper construction of a flying machine. I wish to avail myself of all that is already known and then, if possible, add my mite to help on the future worker who will attain final success.