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
Medical science has proven time and again that when the resources are provided, great progress in the treatment, cure, and prevention of disease can occur.
Where we have good, testable explanations, they then have to be tested, and we drop the ones that fail the tests.
If we do discover more than one type of life on Earth, we can be fairly certain that the universe is teeming with it, for it would be inconceivable that life started twice here but never on all the other earth-like planets.
For I am well aware that scarcely a single point is discussed in this volume on which facts cannot be adduced, often apparently leading to conclusions directly opposite to those at which I have arrived. A fair result can be obtained only by fully stating and balancing the facts and arguments on both sides of each question.
Evolution could so easily be disproved if just a single fossil turned up in the wrong date order. Evolution has passed this test with flying colours.
We didn't build the interstate system to connect New York to Los Angeles because the West Coast was a priority. No, we webbed the highways so people can go to multiple places and invent ways of doing things not thought of by the persons building the roads.