To properly address this question we must consider the label skeptic and the label theist in equally broad terms. To be skeptical sometimes and a theist sometimes is certainly possible, yet does not qualify one a skeptic and theist absolutely. In the broadest sense, the theist believes in the existence of least one god. Only if we define the skeptic as broadly, is it appropriate to ask if it is reasonable to claim to be a theist and skeptic. To be skeptical in only specific, narrowly-defined, instances is an aspect of being human and in no way indicates one is regularly skeptical in his or her daily life. Being a theist, yet rejecting alien abduction for lack of credible evidence, does not make one a skeptic – only skeptical.

In the broadest sense, a skeptic is one who believes a claim only when appropriate evidence and/or argument is given in support. The type of evidence will vary by claim. On the mass, however, a modern skeptic will demand evidence from multiple sources, under differing circumstances (multiple paradigms), by those who have no stake in the outcome. The more rigorous the research, the closer it conforms to the scientific method, the more inclined will be the modern skeptic to accept the claim. Of course, this assumes the skeptic has accepted the scientific method, and specifically, the experiment as the strongest kind of evidence. Nevertheless, it is often not possible to conduct a double-blind, placebo-controlled experiment on a giant randomized subject base due to ethical other issues and complications. Even so, the skeptic demands evidence to be observable, measureable, and repeatable when measured again by others. Evidence which leads to models which are predictive in various situations is stronger yet. If these minimal requirements are not met, the skeptic will reject the claim until a time when more evidence is available. Thus the skeptic is open to examining and re-examining any claim so long as new evidence is presented.

Argument, for the skeptic has to be cogent, and avoid common logical problems. Arguments from authority (no necessity for evidence), moving the goalposts when claims are not borne by evidence and other weak or misleading argument strategies are readily rejected by skeptics. More importantly, and more fundamentally, argument must come from evidence…it cannot be contrary to evidence. Argument must incorporate good evidence, not ignore evidence that is contrary to the position being argued. In other words, the skeptic must not cherry-pick—must not look for supporting and ignore contrary evidence when developing a position on a specific claim.

If this is what it is to be a skeptic, the question becomes, “Is this what it is to be a theist?” Or, “Can one be a theist without violating the skeptic’s demands for evidence and good argument?” To answer this is surprisingly easy when framed in these broad terms. To be a theist is to believe. There is no evidence requirement. To believe in at least one god does not allow one to predict anything we observe. And it does not need to predict anything observable. For the skeptic, the belief in a god—any god, any gods—has nothing to do with anything observable simply because there is no evidence that a god has anything to do with anything observable.

Often it is argued that if one were able to present evidence of the need for a god to explain something, anything, we observe, then a skeptic would by definition have to entertain that evidence and the resulting argument. This, though, is a twisting of lack of evidence into evidence. Simply because one has no complete (or even satisfactory) explanation for a phenomenon, is not evidence for god. Instead this is the definition of a question. For instance, to ask “What caused the big bang,” is a valid question for which there is currently no solid evidence. To then conclude that there must be a god is negative evidentiary stance. God exists because there is no other (better?) explanation. So by the same argument, anytime we lack good observation-based evidence and explanation, we should simply cite a god as explanation. This has the ironic result that the more ignorant we are, the more theistic we should be. God is for the ignorant. Or, if one prefers, in general, as we explain ourselves, our world, our universe more, we diminish our god’s role in each of those areas. The logical error of this argument is to confuse the lack of evidence with evidence. Just because we have no evidence (yet?) for a scientific explanation of the big bang does not by default offer evidence for the existence of a god or gods.

So, do I think you can be a theist and a skeptic? No. Skeptics cannot just believe; they require evidence, and argument from evidence, to believe. Can you be a theist and be skeptical in many, most, or almost all aspects of your life? Sure. Can a religious person be skeptical? Why not? Throughout history, many religious, theistic thinkers have been skeptical, critical, or rational and are responsible for the state of science and skepticism today. To name a few: Thomas Aquinas, Copernicus, Galileo, Kierkegaard, and more recent (some still even alive!) such as Kenneth Miller. Does the skeptical movement need to be puritanical and anti-dogmatic to succeed? No. As a movement, skepticism needs to gain acceptance, not estrange itself from those who would support its principles were scientism’s proponents not so imperious and arrogant. With over 80% of U.S. residents surveyed claiming to be Christian, and only 30,000,000 reporting to be atheist or agnostic, there is little sense preaching to the converted.

What skepticism must fight against is the tendency for people to settle for simplistic explanations, made by the religious, reducing difficult subjects and as-of-yet unexplained phenomena to the realm of the supernatural. The danger is not only that this is intellectually insulting and does nothing to further understanding, but such a position eliminates our personal responsibility to resolve major humanitarian crises and human-made or other global catastrophes.

I offer the closing lines of one of my favorite books on the subject, The Survival of God in the Scientific Age, by Alan Isaacs. “But perhaps our greatest gift to posterity is that we have released our children from the fear of the supernatural. The concept of God is still available for those who need it – those who do not, have no longer to be ashamed and no longer to be afraid.”