“”One of the great tragedies of mankind is that morality has been hijacked by religion.
|—Arthur C. Clarke|
The argument from morality is the apologist argument that God is the source of all morality, and therefore, if objective morality exists, God must exist. A particular form of it is St. Thomas Aquinas's argument that the moral part of the Mosaic Law could be deduced from natural law. A further extension is that all morality comes from scripture, which in turn is the word of God.
 Criticisms of the argument
The argument's justification for proving God's existence is often countered by explaining or postulating naturalistic origins for morality. While there are various secular formulations of morality and ethics, such as humanism, it needs to be explained why we feel morality. Evolutionary advantages for certain behaviors that one could consider "moral", providing an alternative explanation that does not require a god. Evolutionary psychology, when it works properly, attempts to do this. For example, killing another person is detrimental to the society at large; the tribe has one less person to help or defend it. Law enforcement is not perfectly efficient, and morality provides an additional barrier against criminal behaviour. There are also several other specific refutations against the idea that morality comes from God and God alone, as well as logical flaws in using it as an argument for the existence of a divine deity:
- The existence of God is assumed in defining something that already exists (morality); therefore it is circular reasoning by attempting to show the existence of God in this manner.
- The assumption of an omnipotent God leads to problems communicating a moral code in a clear way to people in an authentic manner.
- The argument that morality is "hard-wired" by God (to circumvent the communication problem) implies that this argument is dependent on the argument that direct creation actually happened.
- There are explanations for the origin of morals other than "Goddidit".
- When multiple religions/denominations each use this argument to justify its own version of deity, the credibility of the whole argument weakens. This is because the "objective" morality used for the premise is not exactly the same for each religion/denomination.
- For Abrahamic religions, God's actions aren't exactly what most people can justify as "moral" when they are the ones performing such actions.
 Omnimalevolence vs omnibenevolence
The proponent of this argument must present logical evidence explaining why their God must be omnibenevolent rather than omnimalevolent. This is related to the Euthyphro dilemma; asking if things are good because God says so, or God is good because there is a morality that God follows.
One can choose to have omnibenevolence as part of the definition of God, but this is not necessarily true when considering God as an hypothesis with necessary characteristics and inferred, or desirable, characteristics. Godly traits such as omnipotence and omniscience are substantiated because the God hypothesis necessitates them. For example, for God to create the universe from nothing, creatio ex nihlo'', would necessitate God to be omnipotent and omniscient, we can safely assume these properties of God. So ultimately, the theist must present similar logical evidence that necessitates an omnibenevolent God, rather than an omnimalevolent one, or at least not morally disinterested one. To put it simply, the theist must explain why their god is 'good' rather than 'bad'.
A second possible answer proving God to be benevolent may be that its obviously better for something to be all good than for it to be all bad. But this causes a few more problems. Effectively, the theist has created a morality outside of God (invalidating the argument that God is the source of morality), then assessed God's nature by this standard of morality to conclude that God is 'all good'. This response is patently incoherent as you can't affirm the objectivity of God by first assessing it with subjective standards. This is why any argument for an omnibenevolent God is fantastically idealistic, there is simply no reason why God must be omnibenevolent rather than omnimalevolent.
 Demonstrating the existence of objective morality
The proponent of this argument must demonstrate the essentiality of an objective morality, and thus demonstrate the existence of an objective morality.
An obvious rebuttal would be 'we must have an objective morality to tell right from wrong'. An ostensibly reasonable statement, but sadly it holds no basis in reality. Arguing this line has one major shortcoming. That is, it does not explain why we must distinguish right from wrong, there is no mechanism of essentiality outlined definitively requiring humans to be able to discern right from wrong. Of course, here the theist will object 'that this proves atheists are amoral', but again this holds no basis in reality. Just because something is not essential, does not mean we still don't subscribe to it. In the case of murder, for example, an objective morality dictates that such an act is forbidden. However, humans have long come to know that such an act is reprehensible for purely secular reasons. So to recap, the theist must prove that an objective morality is essential, and then proves the existence of an objective morality, and thus proves the existence of a objective morality generating entity, and finally link their version of God as the sole objective morality generating entity.
Not so much an objection as it is an open question, but to the theist: Is it merely a coincidence that the well-being of sentient creatures, secular subjective morality, and the supposed objective morality of God correlate so strongly?
Using the stages of moral development proposed by Lawrence Kohlberg, it could be suggested that fundamentalists claiming that morality comes from the Bible passes no more than the first, pre-conventional, level. This level cites self-interest and fear of punishment as the driving force for morality, and is most common in children. However, given that fundamentalists respect the authority of the Bible, it could be argued that they are in the second, conventional, level — in which morality is driven by a respect of authority and the social norms it provides.