All experiments are fruitful if you don't have any preconceived notions about the results.
Language has crystallized them into certain definite notions and expressions, without which we cannot proceed a single step, but which we have accepted without knowing their exact meaning, much less their origin.
The object of his metaphysics is so to remodel the current notions regarding the existence of things and their connexions with which the usage of language supplies us as to make them consistent and thinkable.
The world of many things surrounds us; our notions, by which we manage correctly or incorrectly to describe it, are also ready made.
What remains to be done is, not to explain how such a world manages to be what it is, nor how we came to form these notions, but merely this - to expel from the circle and totality of our conceptions those abstract notions which are inconsistent and jarring, or to remodel and define them so that they may constitute a consistent and harmonious view.
How would you define notions? Add your definition here.