In proportion as our faith in these views grows weaker, and the phenomena of the organic or inorganic world presented to us by geology seem explicable on the hypothesis of gradual and insensible changes, varied only by occasional convulsions, on a scale comparable to that witnessed in historical times; and in proportion as it is thought possible that former fluctuations in the organic world may be due to the indefinite Modifiability of species without the necessity of assuming new and independent acts of creation, the number and magnitude of the gaps which still remain, or the extreme imperfection of the record, become more and more striking, and what we possess of the ancient annals of the earth's history appears as nothing when contrasted with that which has been lost.
"The Student's Elements of Geology"
Sir Charles Lyell
The histories of the most civilized nations show us that in their earlier times, the Modifiability of ideas and habits was less than it is at present.
"Essays: Scientific, Political, & Speculative, Vol. I"
Herbert Spencer
5. Mental Modifiability in the two sexes.
"Essays: Scientific, Political, & Speculative, Vol. I"
Herbert Spencer