> Of course, the labels were not so clear at his time. This is understating the issue quite a bit. Don't forget that the point of science is to test things in

> Of course, the labels were not so clear at his time. This is understating the issue quite a bit. Don't forget that the point of science is to test things in a robust manner, which at this point in time has been done for the things you mention, but in Newton's time they hadn't been.