The way some theists talk about the relationship between atheism and value, and atheist can put his bare hand in a bed of hot coals and care nothing about the outcome.
After all, value comes from God. Without a God, nothing can be important or worthwhile. Nothing matters. Clearly, the effects of having one's hand in a bed of hot coals is not at all important - not worth caring about.
Of course, this is nonsense. The universe may not care about me blistering and charring flesh, but I care. I care a great deal.
Furthermore, that caring is a part of the real world. It is as real as the flesh and the fire - and as real as the nerve endings and the brain configuration in which those events reside. Like gravity and magnetic fields, this aversion to the effects of charring flesh has an influence on events in the real world. Specifically, it motivates me to avoid states of affairs in which my flesh is being burned away. We can see this aversion to pain in the behavior of intentional agents, just as we can see a magnetic field in the behavior of iron.
This aversion to pain also motivates me to avoid situations in which I am being burned. It motivates me to install a smoke detector in my home, to keep explosive liquids such as gasoline away from open flames, to avoid buying a car that is prone to bursting into flames when it gets into an accident.
Another set of behavior that I can engage in to reduce the risk of being burned is to motivate others to avoid behavior that might result in my being burned. It gives me a reason to give to others, using whatever social tools are available, an aversion to cruelty. With respect to those other people, their aversion to being burned also gives them a reason to join me in a campaign to promote a society-wide aversion to cruelty.
All of these are facts about the world - regardless of whether or not one believes in a God. A belief in God does not change the fact that a water molecule is made up of one atom of oxygen and two atoms of hydrogen. It does not change the fact that the earth is (roughly) spherical. It does not change the fact that human respiration adds oxygen to the blood stream. It does not change the fact that a strong aversion to pain gives people a reason to use social tools to promote a society-wide aversion to cruelty.
I bring this up in my defense of secularism to address an argument against secularism that says, while secular arguments are great for addressing matters of fact, it cannot address matters of value. Value requires a god, so value claims cannot be secular.
I have been looking at secularism by looking at a wholly secular institution - the institution of a trial. When it comes to establishing the material facts in a trial, only secular arguments are permitted. Religious arguments (i.e., "I have faith in the claim that the accused is guilty" or "God told me that the accused us guilty") are not permitted in a court of law.
However, while it is true that the material facts are established through a presentation of wholly secular evidence, the law itself comes from an outside law giver. The ultimate law giver is God. Consequently, arguments about what the (moral) law states are inherently sectarian. They cannot be secular. We can dispute the material facts of a case all we want using secular arguments, but we cannot discuss the (moral) law without mentioning a god.
My argument above is meant to show that this is not true. An aversion to pain is not dependent on a belief in a god. Neither is its power to motivate pain-avoiding behavior. Nor do we need a god to explain the fact that this pain-avoiding behavior provides (nearly) everybody with a motivating reason to establish a community-wide aversion to acts that could lead to causing such pain.
A similar set if materiel facts surround the community-wide aversion to taking life or taking property - and in favor of community- wide motivation to help others in need and to tell the truth.
One can still accept all of this and still believe that it is the work of a law-giver. One can still say that God created a universe in which there is a moral law, and that moral law can be discovered using wholly secular arguments such as the one presented at the top of this essay. If somebody wants to insist that there is a law-giver behind it, there is nothing that can be said here against that claim.
For example, assume that you and I were in the jury on a case in which a tree fell off of a logging truck and struck a vehicle, killing its occupants. Assume that I believe that trees came about through a long process of evolution, but you believe that God created trees 6000 years ago.
These beliefs have nothing to do with the material facts relevant to the question of whether the accused should be punished for negligence. It does not affect the verdict. Therefore, the fact that we have these different beliefs are materially irrelevant to the case. Nothing about the institution of a trial (where secular arguments only are permitted) has anything to say about your non-secular beliefs regarding the origin of trees.
Similarly, I can believe that humans evolved to have certain desires such as an aversion to pain that generates a motivation to use social tools to promote a society-wide aversion to cruelty. You can believe that a God created a universe in which this relationship exists.
Even in a case that involves a victim forced to endure a great deal of pain, these beliefs that humans were created to feel pain and be averse to the effects - or evolved to feel pain and are averse to the effects - are as irrelevant as beliefs about the origin of trees in the previous example. We both understand pain, and we both understand the motivating reasons that an aversion to pain provides for social institutions condemning cruelty.
Even here, we have not yet found any reason to leave behind the prohibition on religious arguments when determining whether or not to engage in behavior that harms others - such as declaring them guilty of a crime. All of the reasons for prohibiting religious arguments in a court of law remain just as valid when we shift the discussion away from the guilt or innocence of the accused in a trial to the merits and demerits of public policy.