When electrification is produced by friction, or by any other known method, equal quantities of positive and negative electrification are produced … The electrification of a body is therefore a physical quantity capable of measurement … While admitting electricity, as we have now done, to the rank of a physical quantity, we must not too hastily assume that it is, or is not, a substance, or that it is, or is not, a form of energy, or that it belongs to any known category of physical quantities.

The first step is to measure whatever can be easily measured. This is O.K. as far as it goes. The second step is to disregard that which can't be measured or give it an arbitrary quantitative value. This is artificial and misleading. The third step is to presume that what can't be measured easily isn't very important. This is blindness. The fourth step is to say that what can't easily be measured doesn't really exist. This is suicide.