The Moral Argument for the existence of god can take many forms. Here, rather than trying to critique every possible variety, I will deal with Peter Kreeft and Ronald Tacelli’s formulation. They lay it out in the following manner:
- Real moral obligation is a fact. We are really, truly, objectively obligated to do good and avoid evil.
- Either the atheistic view of reality is correct or the “religious” one.
- But the atheistic one is incompatible with there being moral obligation.
- Therefore the “religious” view of reality is correct.
Kreeft and Tacelli admit that “religious” in premise 2 and the conclusion (4) must be read very broadly, and, in the sense that they use the term, the “religious view” is compatible with, among other things, Platonism. Given their chain of reasoning, to be examined presently, the term “atheistic” in premises 2 and 3 might also be better read as “physicalist.” Because of this, it might well be the case that they are not so much arguing for god’s existence as they are arguing against physicalism. I will not dwell on this issue since I believe their argument fails no matter how one interprets the terms.
The argument, if we take “atheistic” and “religious” to be synonymous with “physicalist” and “nonphysicalist,” respectively, is valid. It remains to see if it is sound. Premise 1, the objectivity of moral obligation, is offered without support. The authors accept that the conclusion does not follow if this premise is false; however, I am willing to grant the truth of this premise for the sake of argument (in fact, I believe it to be true). Premise 2, with our reading outlined above, is clearly true. The issue hinges, then, on the truth of premise 3.
Kreeft and Tacelli support premise 3 in the following way:
Now given the fact of moral obligation, a question naturally arises. Does the picture of the world presented by atheism accord with this fact? The answer is no. Atheists never tire of telling us that we are the chance products of the motion of matter–a motion which is purposeless and blind to every human striving. We should take them at their word and ask: Given this picture, in what exactly is the moral good rooted? Moral obligation can hardly be rooted in a material motion blind to purpose.
Nothing in atheism makes it necessary to restrict oneself to a worldview of nothing but blind, purposeless matter and motion, but this accounts for the proffered interpretation of “atheist” as “physicalist.” Further, it is an open question as to whether sentience can exist apart from matter. Since Kreeft and Tacelli are arguing in terms of human morality, and given that humans are material creatures, I will set aside this concern and proceed as if matter is necessary for a coherent discussion of morality. In the end, the question at hand is whether Kreeft and Tacelli have adequately supported the assertion that morality, to the physicalist, can have no objective basis.
Morality has no meaning unless there are (1) beings that are capable of suffering and flourishing and (2) agents (beings who may, at least to some degree, determine their actions and who understand the suffering and flourishing of others); these groups are not identical, though there will be overlap between the two assuming the agents themselves may suffer and flourish. Kreeft and Tacelli accept this, saying “[I]t is hard… to conceive of objective moral principles somehow floating around on their own, apart from any persons.” Indeed, it seems hard to conceive of any moral system at all, objective or otherwise, existing apart from persons, taking “persons” as “agents” (assuming, again, that these agents are capable of suffering and flourishing, or at the very least that there are others capable of suffering and flourishing and that the agents understand this).
Kreeft and Tacelli baldly state that moral obligation cannot be rooted in blind, purposeless material motion, and they may well be correct in asserting this. In any event I will not contest the point. There is a very real question, however, as to whether this is germane to the discussion. Once agents (and possibly other beings within their moral scope) are on the scene and morality becomes a live issue, there is no longer just matter and motion, however blind to purpose it may be; for there to be an intelligible discussion of morality, sentient beings must exist. This means that the relevant matter is neither blind nor purposeless: The agents have plans, goals, hopes, and fears. Kreeft and Tacelli have constructed a strawman argument since no one (of whom I am aware, at any rate) believes morality is based merely in blind, purposeless material motion; it may be argued, however, that it is based on matter and motion plus the ingredient of sentient creatures capable of suffering, flourishing, and/or understanding the suffering and flourishing of themselves and others.
If this is right, then Kreeft and Tacelli seem to be presenting a proposition roughly analogous to “Water is ultimately rooted in hydrogen.” While it is true that hydrogen is necessary for water to exist, it is not sufficient; oxygen is also needed. In a like manner, matter and motion are necessary for morality (at least human morality), but they are not sufficient–sentience is also required. It might be argued that since oxygen is cooked up in stellar interiors from hydrogen, then water is rooted in hydrogen after all (and, more to the point, it may be argued that the physicalist must say sentience is rooted in matter and motion because sentient beings are “cooked” from material motion). This, however, simply isn’t the way we explain (or give the ground of) things. To coherently speak of the ultimate ground of anything, there must be different grounds of different things. What is the ground of baseball? Hydrogen and motion. What is the ground of literature? Hydrogen and motion. What is the ground of medicine? Hydrogen and motion. To speak this way is to give a nonanswer since it is in no way informative. Note, too, the theist is in no better condition: She must say the ultimate ground of baseball, literature, and medicine is god in every case. This is equally unilluminating. But Kreeft and Tacelli must assume there are meaningful answers to be given since they are the ones who asked about ultimate grounds to begin with. I therefore infer that even though matter and motion are necessary for morality, they cannot be said to be the ultimate ground of it. In doing this, I stand shoulder-to-shoulder with Kreeft and Tacelli, but I question why they would imply that a physicalist would make such a claim in the first place.
It remains to show that objective morality can be based on the existence of sentient beings. Kreeft and Tacelli argue that, whatever its basis, absolute morality cannot ultimately arise from a mere desire such as avoiding pain or doing good:
Suppose we say it is rooted in nothing deeper than human willing and desire. In that case, we have no moral standard against which human desires can be judged. For every desire will spring from the same ultimate source–purposeless, pitiless matter. And what becomes of obligation? According to this view, if I say there is an obligation to feed the hungry, I would be stating a fact about my wants and desires and nothing else. I would be saying that I want the hungry to be fed, and that I choose to act on that desire. But this amounts to an admission that neither I nor anyone else is really obliged to feed the hungry–that, in fact, no one has any real obligations at all.
This might best be countered by finding an answer to the question, Why do sentient beings have rights? Further, to be useful, any answer arrived at must be consistent with a physicalist worldview. First it must be reiterated that desires do not arise from mere purposeless, pitiless matter; they come from sentient matter. Matter in the form of persons is a horse of a completely different color from its inert cousin, for if there is only purposeless, pitiless matter, then there is no morality. Next we note that suffering is objectively evil. This is not to say that no good can come from suffering or that no suffering is good for us, or that the right of sentient creatures not to suffer is absolute. Still, for suffering to be good for the sufferer, the evil of the suffering in question must be outweighed by some good that follows from it. Leibniz, for instance, held that this is the best of all possible worlds and if the world were improved in one area, it would be worsened in another–and it would be worse in total; thus, evil is necessary to generate the most good. The important point to note is that suffering must be taken into account in the total tally (Schleiermacher, Hick, and Swinburne, among others, also argue along similar lines).
It is important to note that Kreeft and Tacelli think suffering is evil, too: “[T]he cause of physical evil is spiritual evil. The cause of suffering is sin.” Without sin (spiritual evil), according to Kreeft, we would have “heaven on earth,” where, presumably, there would be no suffering. Kreeft and Tacelli differ with Leibniz in that they do not hold that this is the best of all possible worlds, but what else they believe is revealing. God did not merely create the best of all possible worlds; he built a perfect world. There is no need to speculate whether a perfect world involves any suffering for its inhabitants, because the world was created without sin and, therefore, without suffering. From this, we know suffering is a bad thing (else the world wouldn’t have been perfect without it), but bad for whom? Not god. God, being nonphysical, isn’t the sort of entity that would directly experience physical evil. Even if one wanted to say god has sympathetic psychic pain when his creatures suffer, it can’t be argued that god is the primary victim of suffering. That would be like saying murder is wrong because the victim’s friends will miss her. It also can’t be rocks or trees that suffer because they are not sentient. Suffering is bad for sentient, material creatures because they are sentient, material creatures.
In any case, suffering is bad in its own right. Kreeft and Tacelli say so explicitly, and Leibniz must believe it is an evil because otherwise there would be no need for it to be accounted for and outweighed by the associated good from which it is generated. So why do sentient beings have rights? They have rights because they can suffer. Since it is basic to persons that suffering is evil, then morality, on this view, is objective: “duties arise from the way things really are,” as required by Kreeft and Tacelli. Thus, the argument here is not that morality is based merely on a desire to avoid pain (or any other desire, for that matter), but rather it ultimately springs from objective facts about the character of agents and the nature of suffering.
None of this, of course, goes anywhere in proving that god does not exist. The point here is that the existence of objective morality (if it in fact exists) does not entail the existence of god. Once one recognizes that the evil of suffering is basic to sentient creatures and that morality can spring from them, god isn’t necessary (though, once more, she/he/it might exist anyway). The proposition that objective morality is incompatible with a physicalist orientation is simply false, and since Kreeft and Tacelli’s argument explicitly relies on it, their argument fails.
 Kreeft, P. and R. Tacelli. (1994). Handbook of Christian Apologetics: Hundreds of Answers to Crucial Questions. Madison, WI: InterVarsity Press, 72.