Evaluative or thick conceptions[b] of education state that it is part of the nature of education to lead to some kind of improvement. They contrast with thin conceptions, which provide a value-neutral explanation.[13] Some theorists provide a descriptive conception of education by observing how the term is commonly used in ordinary language. Prescriptive conceptions, by contrast, define what good education is or how education should be practiced.[14] Many thick and prescriptive conceptions see education as an activity that tries to achieve certain aims.[15] Some concentrate on epistemic aims, like knowledge and understanding. Others give more emphasis to the development of skills, like rationality and critical thinking, and character traits, like kindness and honesty.