A usually-moody-looking Ludwig Wittgenstein almost smiles.

According to Ludwig Wittgenstein (pictured), our description of time is a linguistic game. That is, there are two games to choose from: ‘information-time’ and ‘memory-time’.

Information-time refers to a public-chronology—the use of clocks, diaries, calendars, and so forth. However, really, information-time is just a measurement of something else: currently, on Earth, ‘one second’ has been calibrated to mean ‘9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom’.

Memory-time, in contrast, is an arrangement of personal memories which allows us to manage events with personal expectations. Measurement-time, however, is underpinned by subjectivity. For in this game there is only ‘before’ and ‘after’ and ‘earlier’ and later’. There is no ‘past’ and there is no ‘future’, unless someone claims a present.

We usually express memory-time with indexical sentences—references to objects which change with context, rendering it ambiguous. For example, the sentence, ‘Yesterday Bill was in my house,’ could convey a meaning of a human known as Bill being present in the spatiotemporal location of my house; in another context the sentence could refer to my neighbour’s donkey Bill breaking into my tree house. (Both could have occurred half an Earth-spin ago.) Memory-time, then, is a system for internal referencing; it is made to be external with language. But objects can’t be placed in external temporal space because their change can’t be measured with standalone physical criteria.

Yet no matter which kind of time we refer to—which game we play—the sentences we utter about time are deprived of standalone meaning. Both forms of time reference changes in the external world relatively: one is recorded with respect to caesium atoms; the other is founded in subjective recollections.

Wittgenstein warns us to be clear as to which one we are referring to. Without clarity, we’ll have to prioritise one and be forced to confusingly express one with respect to the other.