It is common for Mormons to connect their religious beliefs to the ancient Christian Church of the 1st and 2nd century before the so called "Great Apostasy." Following along with this line of thinking, McMurrin connects Mormonism to the 4th century monk Pelagius, showing how their approach to religion, unlike most modern Christianity, is more naturalistic, finitistic, and humanistic. Furthermore, McMurrin points out that Mormonism is like a melting pot (though he does not use that phrase) in that in borrows much of the language of traditional Christianity and then turning them upside down by redefining them so much that most other Christian sects will refer to Mormons as heretical Christians at best.
Divided into 5 parts, McMurrin starts with metaphysics, or study of prime reality. McMurrin contrasts and explains monism (reality as one substance, a view held by Spinoza) with pluralism (a view held by William James), showing how Mormonism, due to its dualistic belief in the soul, falls in the pluralism category. The priesthood, which McMurrin points out exists independently of God, also shows that strictly speaking Mormons cannot be monists. McMurrin sums up this distinction aptly when he states:
It is perhaps not entirely inaccurate to describe Mormonism as a kind of naturalistic, humanistic, theism. (The Theological Foundations of the Mormon Religion pg.3)Close quote. For this reason, though McMurrin does not state this outright, Mormonism has more in common with scientific naturalists than it does with traditional Christians at times, maybe even most of the time.
Part two moves from prime reality to God himself and his nature within Mormonism. In contrast to an infinite and eternal God as in classical theology, Mormonism embraces a finite conception of God, which means that he came to be God rather than always being God, as within traditional Christianity. A major theme that runs through this book is that Mormonism is simply much different than traditional Chrisitianity, even if Mormonism uses the same vocabulary. The words mean different things.
Part three discusses the doctrine of man is Mormonism, pointing out that while in traditional Christianity man is a contingent being (he could not exist), in Mormonism is a necessary being; he has always existed and it would impossible for him not to exist, although not always in an embodied corporeal form. This is a radical departure from traditional Christianity because what Christianity classically attributes to God (necessary existence) Mormonism attributes to man and to God, which shows how fundamentally different Mormons are from their Christian counterparts.
One of the most common arguments against theism, and Mormonism is not exempt, is the problem of evil. This problem states if there is a God who is perfect, all-knowing, and all-powerful, why is there evil in the world? Traditional Christianity has its answers to the problem, but Mormonism has its own unique answer to it. Because Mormonism affirms free will in a libertarian or compatibilist sense, humans are morally responsible for the moral evils they create, God is not. Second, because God is contingent and powerful but not all powerful, and nature is eternal, natural evil is simply intrinsic to the universe, and is not evil at all. So, in Mormonism the problem of evil is really not much of a problem.
The final section is about whether or not God is a person, and if so whether or not he, she , or it is a person worthy of worship. This is a supplemental essay, since the question of whether God is a person is obvious in both traditional Christianity and Mormonism, but is a purely philosophical argument about the problem. One could finish the book without reading this essay, but I recommend it.
Mormonism, as John Dehlin pointed out, is in its infancy. Traditional Christianity is over 2000 years old, Mormonism is less than 200 years old. It's theology is not as well developed as its historical counterpart; there is no equivalent of Augustine, Anselm, and Thomas Aquinas in Mormonism (although Blake Ostler may be close). However, there are many strengths to Mormonism, and it has a theology that once developed can be as strong as any of the three great monotheism's.
Not only should The Theological Foundations of the Mormon Religion be in every Mormon household, it should be a text for Sunday school. Too many Mormons do not understand their own theology, and how it differs from traditional Christianity, and this short, powerful text is the place to start. A wonderful book.