Abstract

In this paper, some conditions of physical reality are presented. These conditions are, in particular, the conditions of the real physical quantities. The symmetry principles held about reference frames are essential in presenting the conditions. In the stance taken in this paper, gauge symmetry, the different descriptions of the same physical situation, represents what is real. Based on the conditions, the real physical quantities and the real physical descriptions are those that are independent of reference frames. In the rigorous mathematical term, one can say the real physical descriptions are those satisfied with the substantive general covariance requirement (in the Earman’s term).