Whitehead was a proponent of process philosophy, a philosophy of 'becoming' as contrasted with Plato's philosophy of 'being'. This division can be traced back f

Whitehead was a proponent of process philosophy, a philosophy of 'becoming' as contrasted with Plato's philosophy of 'being'. This division can be traced back further to pre-socratic philosophy, i.e. Parmenides (being) and Heraclitus (becoming). Aristotle continued firmly on the same tract as Parmenides and Plato in terms of having a philosophical focus on being, and today we take this type of thinking for granted as it has permeated nearly all of western philosophy and society. Aristotle may have been more prolific but I suspect the quote is referencing this division more than anything else.