"... the International System of Units (SI), which is the modern form of the metric system;"
I like what Gene and Bill have said about this. Here is how I take it. I didn't see the quote in its original context, but it seems to me that it is not intended to be a legalistic definition of the term "metric system". It is explaining what SI is, not the term "metric system". The sentence has the same form as something like "the Honda Civic, which is a high-quality economy car". We are describing the Civic, not economy cars in general. I looked through the BIPM brochure at http://www.bipm.fr/pdf/si-brochure.pdf, and it continually refers to SI, not "the metric system". My impression from this is that the word "metric" is not necessarily intended to be an exact, precisely defined term the way that SI is precisely defined. Look at it another way. If you want to find out what the metric system is, the quote simply says to look at SI, not some other or older system (like cgs or ifp). If you then look at the BIPM brochure to see what SI is, you find that units such as the liter are explicitly allowed. Metric units are, in some fairly simple way, based on the seven base units and the prefixes. Even a unit such as the calorie is based on the gram and the degree Celsius. Non-metric units, on the other hand, tend to be arbitrary (pound, yard, gallon) or empirical (atmosphere, day, hour). I realize the distinction can be a little fuzzy, but that is why "metric system" is not a very precise term. SI is a coherent subset of all metric units. The liter is explicitly allowed for use because it is such a useful unit (as well as entrenched). Without it, we would need to give a special name to the cubic meter and buy soft drinks in thousandths or millionths of the unit. It would work, but it isn't that important to maintain theoretical perfection. It is simply better (more practical) for everyday use to define the liter as a cubic decimeter. At any rate, it is unquestionably metric, and it won't be abandoned or changed. >I am not worried about ridicule, only accuracy. I am merely >attempting logical interpretation of CGPM statements (and >logical inversions). I think if you want that level of precision, you should just say "SI" because it is known exactly what that means. Carl
