Also our knowledge of the passage of nature assures us that this relation distributes the moments of the family into a serial order.

I abstain from enumerating the definite properties which secure this result, I have enumerated them in my recently published book[6] to which I have already referred.

Furthermore the passage of nature enables us to know that one direction along the series corresponds to passage into the future and the other direction corresponds to retrogression towards the past.
[6] Cf.

_Enquiry_.
Such an ordered series of moments is what we mean by time defined as a series.

Each element of the series exhibits an instantaneous state of nature.