We herein explain the phase of spin glass by reference to finite block spin theory, in which the phase of the spin glass may be considered as being a ferromagnetic ordering between block spins comprised of random spins that have a majority of individual spins in a given sense. By making use of the Curie law of block spins, we obtained the magnetization, susceptibility, and specific heat for the lower and higher temperature approximations of the Brillouin function. Both the susceptibility and the specific heat thus obtained are in good agreement with existing experimental data, although in the latter case the agreement is less convincing near absolute zero temperature. (C) 2009 Elsevier Ltd. All rights reserved.