Many theists think, and argue, that God must exist for objective morality to exist.
This claim can be interpreted more than one way. When arguing with theists, it is shrewd, for purposes of honesty, clarity, and strategy, to point this out. One reason is the following: Psychologically it seems that quite often people are committed to certain propositions more than they are committed to particular interpretations of those propositions. So, a given theist may be adamant about affirming that God is necessary for there to be objective morality but persuadable that some things that could be meant by that statement are not necessary. What ultimately matters to them to maintain, psychologically and theologically, in order to not feel like they are losing a key, identity-forming belief, is that something about morality requires God. Getting someone to abandon their belief in God is very difficult. Getting them to moderate their interpretation of their faith or to interpret an aspect of their faith they had not thought through yet in a more rational, rather than less rational, way is much easier by comparison. And this is a perfect topic to attempt to do that with.
The key distinction to stress is the following: how morality is explained vs. how it is discoverable. There are Christian philosophers who do grant that morality is a matter of rational discovery without reference to Scriptural revelation. In fact, if you are talking to Catholics, you can point right to Thomas Aquinas, the official philosopher of the Catholic Church who believed that Aristotle, though a non-Christian, was not only able to know about morality but to have to understood it in the most philosophically accurate of ways. Aquinas believed in “virtuous pagans”, which is Medieval speak for what contemporary atheists call “people who are good without God”. (He just argued that non-believers could not know the supposedly “supernatural” virtues of “faith, hope, and love”.) Even some contemporary analytic moral philosophers are both committed evangelical Christians and moral realists who believe that moral knowledge is possible, irrespective of religious beliefs. It is not uncommon in any area of contemporary philosophy to find theists who don’t bring God into their philosophical investigations any more than personally theistic scientists or mathematicians do. Being a theist does not have to mean believing that invoking God illuminates every possible question out there and innumerable competent theistic academics and scientists reflexively understand this.
So there is no reason that a theist has to claim that God makes knowledge of morality or motivation to be moral dependent on being a theist—even if they still want to claim that God has to exist in order to create objective morality. This is easy to understand with analogies to logic and science. As far as I know, no theists deny that atheists are capable of grasping logical concepts or doing science. Some theists argue that the world would not in fact be logical and orderly in the ways that logic and science could explicate were there no God and so we need to believe in God to make rational sense of how it is that we can know things. But, nonetheless, our minds are manifestly equipped with logical categories and we have manifestly developed amazing powers of scientific discovery and confirmation and technological application. So we can and do know many things without referencing God–even if metaphysically we would be (supposedly) required to posit God to explain how all that order is possible.
So theists can interpret objective morality’s supposed dependence on God similarly. They can say that God is somehow an explanatory principle in why morality is true while granting that atheists (or people of different religions from their own) are able to use their reason to understand what morality is and that it is true. So, just as an atheist or people who worship wrong gods (or who wrongly understand God) can nonetheless grasp that laws of logic and findings of science are true but not know “why” they are true since that supposedly entails God, they can know and be motivated by moraliy similarly.
I think that God is in fact a demonstrably superfluous concept that does not in fact explain why morality, logic, or science are objectively binding. I think that positing a superpowerful mind that creates logic and order does not explain anything since that being itself would be subject to logic and order. Logical order seem to be the basic, brute (and marvelous!) fact of reality—if such a thing can be known at all with our feeble minds. Positing a super-mind does nothing to solve the problem. It just seems anthropomorphic and to superfluously add an extra, totally unproven, mind even more mysterious than our own to account for, without any independent evidence.
Nonetheless, if theism is not going to vanish after reading that last paragraph, I would rather theists at least shift en masse to the position that God explains the existence of morality rather than continue to make the even falser and more Othering charge that atheists or people with a wrong understanding of God cannot know anything about morality or be moral. Convincing the theist to shift the claim makes it a more academic one and less of an insulting one. It allows that there really is no great and terrifying threat from the atheist neighbor or politician. She can know and be motivated by morality too even if she (supposedly) cannot give as coherent an account of why it has truth as the theist (supposedly) can.
In fact, to impress this upon theists, we can point out that their attempts to convince atheists we need their God for morality to be true actually assume that we are people who know all about morality and are deeply invested in it. If we were amoral or immoral people, why would we be phased by their leaping up and down insisting that without God no one can know morality or be morally motivated? Why would that scare us? Implicitly, they know we know all about morality and care a great deal about it, just like they do. So point that out to them.
Finally, two important challenges I regularly like to make—one for theists and one for atheists. I like to challenge theists who attempt to convince atheists that if there is no morality why they want to use that gambit when, at least on the accusing theist’s own perspective, convincing an atheist that there is no reason to be moral might encourage the atheist to be amoral or immoral in his or her actions. The theist who argues that way, on her own terms, is risking convincing the atheist to be a worse person. The theist would rather use this scare tactic knowing that it is possible an atheist might say, “well I still see no objective reasons to believe in God, but now I also have no objective reasons to be moral either!” Why not, if you genuinely care about morality and not just creating converts using any tactics possible, affirm and encourage the atheist’s grasp of morality and then appeal to us on this common ground. That has the advantage of both making us feel respected, appealing to the morally conscientious side of our nature, and reinforcing our commitment to being moral generally. Not only is this approach more honest and less insulting, it serves morality itself much better and makes atheists more receptive than attempts to manipulatively demonize us.
And my challenge to atheists is simple: we need to be careful about when we get offended. There is a difference between a theist who says offensive and blatantly false things like “because you are an atheist you must be a bad person” or “if you were consistent in your atheism you would be a bad person”, on the one hand, and someone who simply calls for us to give good, rational explanations of our views on the foundations of morality. Someone who says that logic, science, or morality require a God to explain their truth is not thereby insulting atheists.
When a theist challenges us to justify our commitments to our specific moral principles in objective terms or to explain why morality has fundamental validity at all or accuses us of having an incoherent or contradictory understanding of the foundations of morality, logic, or science, these are not, in themselves, personal attacks. Sometimes they come mixed in with anti-atheist prejudices or personal attacks but they are not themselves personal attacks. I think they are wrong arguments. But they are not causes for personal offense any more than our challenges to theists that their beliefs are contradictory or incoherent are.
We rightly feel free to demand of theists that they distance themselves from their beliefs enough that they not take it personally when we charge that their view of the world is inconsistent, contradictory, incoherent, or refuted by philosophy science, history, probability, or various other facts. We need to be equally goodnatured, rather than offended, and give good rational arguments when they demand of us a coherent metaphysics, philosophy of science, philosophy of logic, or metaethics. We also need to accept that their calls for moral theory are legitimate. And there already exist a great deal of insights into moral theory that have nothing to do with gods. Cutting edge moral philosophy is robustly secular and rich in insights. We should be educated in them and explain constructively. It is an opportunity for dialogue and education in secular thinking so that people grasp what their options outside of religious thinking are.
The average atheist may not be well educated in moral philosophy and this may explain why atheists often simplistically wave away serious, complicated questions of the foundations of morality as oh-so-easily-solved or evade the issue entirely by switching the subject to personal offense instead of taking the philosophical problems seriously. What is required is atheists be humbler and engage moral philosophy more rigorously instead of evading the hard work and patience involved in all of that with hand waving, crude over-simplificaions, and imprecise personal outrage.
More strategies for debating theists: 13 Practical Strategies For Arguing With Religious Moderates
For my arguments against a theist who claimed she had to become a Catholic in order to account for her belief in morality consistently, see In Which I Answer Leah Libresco’s Moral Philosophy Concerns So You Don’t Become A Catholic Too
For a long but nearly thorough and definitive statement of my views on the foundations of morality see My Systematic, Naturalistic Empowerment Ethics, With Applications to Tyrants, the Differently Abled, and LGBT People
For my responses to the notion that God could guarantee objective morality, see God and Goodness and/or On The Incoherence Of Divine Command Theory And Why Even If God DID Make Things Good And Bad, Faith-Based Religions Would Still Be Irrelevant
For more on my challenges to theists not to try to convince atheists they need to be theists to be moral see For God or Morality? On Those Who’d Hold Morality Hostage For Faith
For more of my challenge to atheists not to conflate philosophical challenges that we have explain our moral philosophy coherently with demonization of atheists or personal attacks, see the post Being Personally Moral Is Not Enough, Atheists Need A Coherent Metaethics.