Ethics - The Original Classic Edition. Spinoza Benedictus

Proof.--This proposition is self--evident, for so long as the human body continues to be thus affected, so long will the human mind

       (II. xii.) regard this modification of the body--that is (by the last Prop.), it will have the idea of the mode as actually existing, and this idea involves the nature of the external body. In other words, it will have the idea which does not exclude, but postulates the existence or presence of the nature of the external body; therefore the mind (by II. xvi., Coroll. i.) will regard the external body as actually existing, until it is affected, &c. Q.E.D.

       Corollary.--The mind is able to regard as present external bodies, by which the human body has once been affected, even though they be no longer in existence or present.

       Proof.--When external bodies determine the fluid parts of the human body, so that they often impinge on the softer parts, they change the surface of the last named (Post. v.); hence (Ax. ii., after the Coroll. of Lemma iii.) they are refracted therefrom in a different manner from that which they followed before such change; and, further, when afterwards they impinge on the new surfaces by their own spontaneous movement, they will be refracted in the same manner, as though they had been impelled towards those