 First, […] we experience in ourselves that we form in our mind new concepts of many propositions and conclusions. These concepts remain in us later and we return to them when we want to remember such propositions. […] Second, […] from individuals seen or imagined by us we abstract and form defining characterizations of their universal features […] and we come back to these when we wish to view such universal features. (Tractatus de verbo 6.2.3)