"But the problem is that objective values do exist, and deep down we all know it.
There's not more reason to deny the objective reality of moral values than the
objective reality of the physical world."¹

Locating objective morality in any of the books of the Old Testament is arduous at best. Despite the supposedly absolute commandment "Thou shalt not kill", Yahweh butchered 70,000 men because David took a census,² ordered the Israelites to kill the inhabitants of the Promised Land,³ and commanded Saul to obliterate the Amalekites.⁴ The punishment of death is to be administered to anyone guilty of picking up sticks on the sabbath,⁵ cursing their parents,⁶ or being raped while betrothed.⁷ Babies are to be cannibalised,⁸ drowned,⁹ sacrificed,10 and dashed against rocks.¹¹

Apologists circumnavigate this moral incongruity by arguing that these are difficulties of moral epistemology or semantics and are irrelevant to the ultimate source of objective values. A supernatural moral ontology however faces the following dilemma.¹² Does a god approve of an act because it is good or is it good because a god approves of it? Does objective morality exist independently of a divine creator or is it formulated by him or them?

That there are moral standards independent of a god's command was accepted by Socrates, the Mu'tazilah school of Islamic scholarship, Averroes, Thomas Aquinas, and Leibniz. However, if there are moral standards independent of that god's will then there is something over which he is not sovereign. He did not establish morality but is held accountable to it and is thus not omnipotent. That particular deity's goodness is not an innate part of his nature but is contingent upon the extent to which he conforms to this independent criterion of "goodness" and one must ask the question of whether through genocide, the advocation of rape, slavery, and stoning, Yahweh has not fallen far short of this standard.

The alternative option was embraced by such thinkers as Martin Luther, John Calvin, Descartes, Thomas Hobbes, William Lane Craig, and Islamic theologians Ash'arite and al-Ghazali. They assert that something is good because their god approves of it. In answer to why the Judeo-Christian god commanded the Israelites to slaughter the Canaanites, William Lane Craig says the following:

"Since our moral duties are determined by God's command, it is commanding someone to do something which, in the absence of a divine command, would have been murder. The act was morally obligatory for the Israeli soldiers in virtue of God's command, even though, had they undertaken it under their own initiative, it would have been wrong."¹³

An act is, in itself, neither moral or immoral. Its virtuousness is determined by its accordance with Yahweh's will. This, Craig argues, is why atheists are perfectly capable of living moral lives, and why theists are capable of heinous immorality. The atheist has aligned himself with the Christian god's approval accidentally and without his determination to do so, the theist believes he is complying with his god's will but is mistaken.

If butchering the Canaanites was virtuous because it was willed by the Judeo-Christian god, then morality is founded upon the subjective feelings of a Divine Creator. It is established upon caprice. Any right action could have been wrong, if Yahweh had so decided. An action that is virtuous today could become nefarious tomorrow. As Leibniz succinctly put it:

"what cause could one have to praise him for what he does, if in doing something quite different he would have done equally well?"¹⁴

If we define "good" as that which a god commands then attributing goodness to that god himself is meaningless. If "good" is "whatever that god approves of" then to say "God is good" asserts nothing besides "God approves of himself no matter what he does." Morality is based not on an objective foundation but on a subjective whim where anything could be right or wrong.

William Lane Craig argues that if naturalism is true, it becomes impossible to condemn war or oppression on the one hand, and then argues that war and oppression is good when commanded by a god on the other. A supernatural moral ontology renders only logical absurdities and not objectivity. Either the god in question is not omnipotent and (quite possibly) immoral, or morality is founded upon the subjective whim of that particular deity and is relative to different situations and civilisations. Many religious people would not put to death apostates, those who work on the Sabbath, children for cursing their parents, or betrothed women for being raped. Electing to follow some moral commandments while ignoring others is not indicant of an objective morality.

Craig argues that the whole moral duty can be summed up by loving God and thy neighbour.¹⁵ Indeed, in Leviticus it is written that: 

"Thou shalt not avenge, nor bear any grudge against the children of thy people, but thou shalt love thy neighbour as thyself."¹⁶

In other translations the people whom are not to be killed are rendered as "the sons of your own people (Revised Standard Version) and "your countrymen" (Tanakh). The prohibition on killing is limited to the people of Israel. In Deut 5:17 Abraham's god proclaims "Thou shalt not kill" and fifteen chapters later in Deut 20:10 he commands the Israelites to sack a city, steal their cattle, enslave those that surrender, rape the women who refuse and kill all the men. Either the commandment is relative or Yahweh is forgetful.

If we entertain the possibility that the commandments were written by mortal men attempting to survive in a cruel and barbaric world then the contradiction becomes clear. The slaughter of whole populations was not Good because it was in accordance with their god's will. It was advocated because it benefited the Israelites.

Morality evolved as mechanisms of increasing group cohesion and reducing vulnerability by behavioural modification or restrain.¹⁷ The desire to be moral -- to be accepted by the group -- is an integral part of human nature. It is an evolved tendency like hunger, thirst, jealousy, love and sexual desire. Morality is not absolute -- but it is objective because it transcends the individual.¹⁸

Claiming that without a god there can be no morality is akin to saying that without a god there can be no hunger. While there are differences of opinion with regard to what is palatable, there is also a general agreement that certain things are not and so it is with morality. Some actions are generally regarded as heinous, others are more culturally and temporally relative.

Morality does not depend upon religion, the supernatural, holy texts or purported prophets for its foundation. It was not created by us but genetically inherited and it is modified by the temporal-cultural circumstances in which we find ourselves. Religion built upon these naturally occurring sentiments by expanding the social scrutiny of individual behaviour to include supernatural agents such as watchful gods, spirits and ancestors.¹⁹ While specific moral values are dispersed along a spectrum of objectivity, morality itself, the desire to be moral, is objective. It is hard-wired into our nature through natural selection.

Theism fails, both ontologically and epistemologically, to sustain an objective morality. The former results in logical incongruity and the latter's inadequacy is revealed by the moral relativity within scripture and in its interpretations. Although morality is held up as a tabernacle of a particular deity's essence, the moral instinct itself, when examined under the cobwebs of dogma, indoctrination and disingenuous apologetics, is discovered where it has always been -- it is located within our nature as social animals.

References:

1 Craig, William Lane. Does God Exist
2 2 Sam 24:1-15
3 Deut 7:2
4 1 Sam 15:3
5 Num 15:32-36
6 Leviticus 20:9
7 Deut 22:23-24
8 Jer 19:9
9 Genesis 7:21-22
10 Exodus 22:29-39 Ezekiel 20:25-26
11 Ps 137:9 Isaiah 13:16
12 Plato. Euthyphro
13 Craig, William Lane. The Slaughter of the Canaanites
14 Leibniz, Gottfried Wilhelm. Theodicy.
15 Craig, William Lane. Can We Be Good Without God?
16 Lev 19:18
17 Dunbar, R. “The Social Brain Hypothesis and its Implications for Social Evolution” Annals of Human Biology.
18 Shermer, Michael. The Science of Good and Evil: Why People Cheat, Gossip, Care, Share, and Follow the Golden Rule
19 Rutherford, M. The Evolution of Morality. University of Glasgow