The Scottish philosopher David Hume argued along these lines: If there is a necessary being—call it Yahweh, then “Yahweh exists” is a necessary truth, a truth that cannot be false under any circumstances. But a truth is necessary only if its denial is logically inconsistent (explicitly or by implication). For example, “All sisters are female” is a necessary truth. Its denial, “Not all sisters are female” implies “Some sisters are not female” which is equivalent to “Some female siblings are not female” (which is obviously logically inconsistent). But consider existential statements such as “Unicorns exist.” Its denial, “Unicorns do not exist,” is clearly not logically inconsistent. The same goes for “Odin exists” and presumably also for “Yahweh exists.” So, “Yahweh exists” is not a necessary truth and Yahweh is not a necessary being.
While Hume’s argument has some initial plausibility, his reasoning rests on a false assumption about necessity. The denial of a necessary truth is a necessary falsehood, a statement that cannot be true in any circumstances. And it is now widely recognized among philosophers that not every necessary falsehood is logically inconsistent. Examples include: “Red is not a color,” “2 + 2 = 22,” “Some blue objects have no size,” “Abraham Lincoln is the number 13,” and “Water is not H20.” Statements such as these describe impossibilities, but one cannot derive a logical inconsistency (“A and not A”) from them. Thus, Hume’s argument rests on a misunderstanding about necessity.
Now, consider all of the contingent beings—a vast number of entities. What explains their existence? Let’s start with the currently living animals and plants. Naturally, we can explain their existence by appealing to biological reproduction. But the currently living animals and plants are preceded by a very long chain of causes. That chain of causes goes back beyond the time when life was first present on earth (roughly 3.5 billion years ago, according to contemporary science). Indeed, that chain of causes presumably goes all the way back to the so-called Big Bang about 13.7 billion years ago. Furthermore, as far as we can tell, all the entities in this chain of physical causes are contingent beings.
How does naturalism explain the presence of contingent beings—not this or that contingent being, but the very presence of contingent beings? In fact, naturalists typically offer no explanation. They typically claim that the existence of physical reality (and hence the existence of contingent beings) is a brute fact, i.e., a fact that cannot be explained. They simply take the existence of physical reality for granted--they do not explain its presence. And notice that nothing would be gained by postulating (hypothesizing) the existence of additional contingent beings. We cannot explain the presence of a type of being simply by postulating that there are more beings of that type!
How does theism explain the presence of contingent beings? Theism explains their presence as ultimately due to God’s choice. But to understand this explanation, we must think about a more fundamental issue: Why would God create anything? Here we must recall the content of the theistic hypothesis under consideration, which includes the idea that God is perfectly good--an idea with far-reaching implications. If God is perfectly good, then God is perfectly loving. And a loving being is generous. A generous being wants to share good things with many others. And a powerful God could share many wonderful things, such as the experience of beauty, the delight in creative activity, the satisfaction of loving personal relationships, the joy of acquiring knowledge, and pleasures--both physical and mental. But of course, to share these good things with many others, God must create many others. Thus, a loving, generous God would have good reason to create many intelligent conscious beings with whom to share good things, beings such as humans. Of course, God might also have reason to create non-physical intelligent beings, such as angels. But embodied, intelligent creatures could certainly be recipients of many good gifts from God. Moreover, embodied, intelligent creatures would plausibly be the most remarkable feature of a physical universe, its crowning feature. And God would have multiple reasons to create the physical universe. First, the universe is spectacularly beautiful—from the starry heavens to the intricate microscopic structures within a cell. Second, the stability of the universe makes it a suitable theatre for the action of free agents. (Just consider how our actions presuppose the stability or regularity of our environment. For example, in a simple act such as handing a child a toy, we must take it for granted that the toy won’t suddenly evaporate and that our arms and hands will do what we want them to do.) Third, the universe is, so to speak, an engineering marvel, fascinating in the way it works. To sum up, theists can explain the presence of contingent beings in terms of reasons a generous God would have to create a physical reality that includes intelligent conscious creatures.