“I've been mulling over something that I know would get thrown in my face if I ever discussed my atheism with certain members of my family. That is the notion that science and rational thought are a work of Satan … that he is the one putting all these rational thoughts in our heads.”
My reply follows:
This kind of “argument" comes from the most profoundly religiously infected. No matter what you do to disprove it with reason, since reason is the enemy of faith, their rejection of reality will be unmoved.
First, understand that the underlying distrust and hatred toward science by the most religious is rooted in their fear that science disproves god. But science doesn't seek to disprove god. Science shows that the things attributed to god/gods/ supernaturalism are more easily explained by physics, chemistry, biology, etc. etc ... natural law and observable repeatable principles. If people wish to reject what they can see for what they can't, science doesn't care one way or another. Science doesn’t waste it’s time on fairy tales or fools.
But let’s go to the devil, so to speak. If a devil is responsible for putting rational thoughts in man's minds then Satan must have been responsible for the invention of small pox vaccine; polio vaccine; heart, lung, liver, etc. transplants; medicines to control diabetes; chemo therapy to save the lives of cancer patients; Lasik surgery to restore eyesight; and the countless discoveries and inventions that have reduced human suffering and extended the lives of theists and non-theists alike. All of which are as a result of the rational human mind; the minds of men and women who were not satisfied with "it's God's Will."
If these rational discoveries by rational people are the influence of an evil entity, then perhaps the devil is good and it is god that is evil. For if god is responsible for the creation of all life forms (Genesis), and is responsible for all the good and evil on earth (Isaiah 45:7), then it was god who created the hideous life forms we know as smallpox and polio. If the devil was the root for rational thought which gave man the power of science that defeated god's evil disease creations, then maybe the Satan worshipers are right.
But again, the problem you will encounter in argument with your fundie family members will be that they aren't held to any definitive limitations. That is, if you blunt their illogic and show a rational reason why their position is fallacy, nothing stops them from inventing a new supernatural justification. You know how that works, we’ve seen it time and again: i.e. "Uh, well maybe all the animals on the Ark were babies and didn’t take up much space or need food, or ... uh, or maybe god put them into hibernation so they wouldn't poop or eat each other ,or … uh . .." And on it goes. When all else falls, the default to the usual ... "God did it, and God can do anything." negates any potential for fruitful exchange.
In the case of Science & Rationality = Satan they may proffer that man was responsible for the creation of virus, and illness, and that god gave scientists the rationality necessary to cure them. But again, what is the basis for that reversal? What scripture will they distort and interpret to support it? It flies in the face of their original premise of rationality and science being the work of Satan.
We the rational are at a disadvantage in these kinds of theological masturbatory discussions. We hold ourselves to, are limited to, strict observable and predictable and repeatable events ... the very definitive guidelines of natural law and science. We can’t adjust our argument by begging some supernatural “shoulda, coulda, woulda” explanation. We are held to real world explanations that we know are scientifically sound.
A word of advice -- you will not convince your family with any argument from reason or reality. The hypnotic grasp of the God Virus is not that easily cured. If anything it will intensify their defensiveness of the indefensible. Do not risk alienating your family for the sake of being right. In the words of Crosby, Stills, Nash and Young, “… just look at them and sigh, and know they love you.”