Thomas Aquinas

“ For movement increases by an addition either to the time it lasts, or to the course it follows: and yet the species remains the same on account of the oneness of the term. Yet movement increases the intensity as to participation in its subject: i.e. in so far as the same movement can be executed more or less speedily or readily. In like manner, science can increase in itself by addition; thus when anyone learns several conclusions of geometry, the same specific habit of science increases in that man. ”

“ The cause that increases a habit, always effects something in the subject, but not a new form. But it causes the subject to partake more perfectly of a pre-existing form, or it makes the form to extend further.
Reply to Objection 3: What is not already white, is potentially white, as not yet possessing the form of whiteness: hence the agent causes a new form in the subject. But that which is less hot or white, is not in potentiality to those forms, since it has them already actually: but it is in potentiality to a perfect mode of participation ”

“ I answer that, Increase, like other things pertaining to quantity, is transferred from bodily quantities to intelligible spiritual things, on account of the natural connection of the intellect with corporeal things, which come under the imagination. Now in corporeal quantities, a thing is said to be great, according as it reaches the perfection of quantity due to it; wherefore a certain quantity is reputed great in man, which is not reputed great in an elephant. ”

“ Further, those things which can be more or less are subject to alteration: for that which from being less hot becomes more hot, is said to be altered. But in habits there is no alteration, as is proved in Phys. ”