""To readers: Length and time are primary because they are naturally fundamental indefinable properties. They are indefinable because they are the properties of empirical evidence.""
"No they're not. Meter sticks don't come with pre-marked gradations, and clocks don't come with pre-marked faces."
The sticks and clocks aren't primary nor are their markings. What is primary is object length and action timing so that acceleration can be recorded and evaluated for meaning. The sticks, clocks and their markings are tools. We can decide on different versions or choices of 'sticks' and 'clocks' don't need faces.
James Putnam