 We conceive of a magnitude as a vector, i.e. as an operation, i.e. as a descriptive function in the sense of ∗30. Thus for example, we shall so define our terms that 1 gramme would not be a magnitude, but the difference between 2 grammes and 1 gramme would be a magnitude, i.e. the relation “+1 gramme” would be a magnitude. On the other hand a centimetre and a second would both be magnitudes according to our definition, because distances in space and time are vectors.…