This character can be defined by quantitative expressions expressing relations between various quantities intrinsic to the event or between such quantities and other quantities intrinsic to other events.

In the case of events of considerable spatio-temporal extension this set of quantitative expressions is of bewildering complexity.

If e be an event, let us denote by q( e) the set of quantitative expressions defining its character including its connexions with the rest of nature.
Let e_1, e_2, e_3, etc.

be an abstractive set, the members being so arranged that each member such as e_{n} extends over all the succeeding members such as e_{n+1}, e_{n+2} and so on.

Then corresponding to the series e_1, e_2, e_3, ..., e_{n}, e_{n+1}, ..., there is the series q( e_1), q( e_2), q( e_3), ..., q( e_{n}), q( e_{n+1}), ....
Call the series of events s and the series of quantitative expressions q( s).