Isaac on Time

“I consider time as flowing or increasing by continual flux & other quantities as increasing continually in time & from ye fluxion of time I give the name of fluxions to the velocitys wth wch all other quantities increase. ...I expose time by any quantity flowing uniformly and represent its fluxion by an unit, & the fluxions of other quantities I represent by any other fit symbols... This Method is derived immediately from Nature her self.”

“Hitherto I have laid down the definitions of such words as are less known, and explained the sense in which I would have them to be understood in the following discourse. I do not define time, space, place and motion, as being well known at all. Only I must observe, that the vulgar conceive those quantities under no other notions but from the relation they bear to sensible objects. And thence arise certain prejudices, for the removing of which, it will be convenient to distinguish them into absolute and relative, true and apparent, mathematical and common. I. Absolute, true and mathematical time, of itself, and from its own nature, flows equably without regard to anything external, and by another name is called duration: relative, apparent and common time is some sensible and external (whether accurate or unequable) measure of duration by means of motion, which is commonly used instead of true time; such as an hour, a day, a month or a year.”

“[T]he Quantity of motive Force cannot be known without Time... Time (...abstractedly) is the continuance of any Thing in its own Being. ...Time absolutely... is Quantity, as admitting... Equality, Inequality, and Proportion... [Y]ou may ask, whether Time was not before the World was created? And if Time does not flow in the Extramundane Space, where nothing is: A mere Vacuum? ..[S]ince there was Space before the World was created, and... there now is an Extramundane, infinite Space, (where God is present)... Time existed before the World began... Some Sun might have given Light long before; and at present this, or some other like it, may diffuse Light thro' Imaginary Spaces. Time therefore does not imply an actual Existence, but only the Capacity or Possibility of the Continuance of Existence; just as Space expresses the Capacity of a Magnitude contain'd in it. ...[D]oes not Time imply Motion? I answer no... any more than it does Rest. ...[W]hether Things move on, or stand still; whether we sleep or wake, Time flows perpetually with an equal Tenor.”

“Time is... a Quantum in itself, tho' in Order to find the Quantity of it, we... call in Motion... as a Measure... and thus Time as measurable signifies Motion; for if all Things were to continue at Rest, it would be impossible to find out... how much Time has elaps'd... We perceive nothing, unless so far as we may be instigated by some Change affecting the Senses, or that our Souls are mov'd and excited by the internal Operation of the Mind. ...So that the Quantity of Time so far as we can observe; depends upon the Extension of Motion. ...It cannot be justly inferr'd... We do not perceive the Thing, therefore there is no such Thing, that is a false Illusion, a deceitful Dream, that wou'd cause us to join together two remote Instants of Time. But nevertheless this is very True... That is, for as much Motion as there was, so much Time seems to have been elapsed; nor, when we mention such a Quantity of Time, do we merely mean any Thing else, than the Performance of so much Motion, to the continued successive Extension of which we imagine the Permanency as Things is co-extended.”