|| D1 || By that which is self-caused , I mean that whose essence involves existence ; or that whose nature can be conceived only as existing .

|| D2 || A thing is said to be finite in its own kind , when it can be limited by another thing of the same nature ; for example , a body is said to be finite because we can always conceive of another body greater than it . So , too , a thought is limited by another thought . But body is not limited by thought , nor thought by body .

|| D3 || By substance , I mean that which is in itself , and is conceived through itself ; that is , that the conception of which does not require the conception of another thing from which it has to be formed .

|| D4 || By attribute , I mean that which the intellect perceives of substance as constituting its essence .

|| D5 || By mode , I mean the affections of substance ; that is , that which is in something else and is conceived through something else .

|| D6 || By GOD , I mean an absolutely infinite being ; that is , substance consisting of infinite attributes , each of which expresses eternal and infinite essence .

|| EXP || I say " absolutely infinite " , not " infinite in its kind " . For if a thing is only infinite in its kind , one may deny that it has infinite attributes . But if a thing is absolutely infinite , whatever expresses essence and does not involve any negation belongs to its essence .

|| D7 || That thing is said to be free , which exists solely from the necessity of its own nature , and is determined to action by itself alone . A thing is said to be necessary or rather , constrained , if it is determined by another thing to exist and to act in a definite and determinate way .

|| D8 || By eternity , I mean existence itself , insofar as it is conceived as necessarily following solely from the definition of an eternal thing .

|| EXP || For such existence is conceived as an eternal truth , just as is the essence of the thing , and therefore cannot be explicated through duration or time , even if duration be conceived as without beginning and end .

|| AXIOMS ||

|| A1 || All things that are , are either in themselves or in something else .

|| A2 || That which cannot be conceived through another thing must be conceived through itself .

|| A3 || From a given determinate cause there necessarily follows an effect ; on the other hand , if there be no determinate cause , it is impossible that an effect should follow .

|| A4 || The knowledge of an effect depends on , and involves , the knowledge of the cause .

|| A5 || Things which have nothing in common with each other cannot be understood through each other ; that is , the conception of the one does not involve the conception of the other .

|| A6 || A true idea must agree with that of which it is the idea .

|| A7 || If a thing can be conceived as not existing , its essence does not involve existence .