Even Spencer by 1865 was admitting that his definition was imperfect, but it remained popular throughout the nineteenth century before declining under the criticisms of William James and others.
Porén, mesmo o propio Spencer en 1865 admitiu que esta definición era imperfecta, pero seguiu sendo popular ao longo do século XIX antes de que empezase a declinar coas críticas que lle fixeron William James e outros.