Arguments may be classified as deductive or inductive. Deductive arguments assert or imply that the conclusion follows necessarily from the premises. Inductive arguments assert or imply that the conclusion follows with some degree of probability, not necessity. Deductive arguments are evaluated for validity. If the conclusion of a deductive argument follows necessarily from the premises, the argument is said to be valid. If the conclusion of a deductive argument does not follow with necessity from the premises, the argument is said to be invalid. Validity is determined by the form of the argument, not the truth or falsity of the premises or the conclusion.....

Inductive arguments may be evaluated by their form, but usually they are evaluated by other criteria. The fallacies of induction are called informal fallacies because they do not evaluate the form to determine validity.

Everything that begins to exist has a cause

The universe began to exist

Therefor, the universe has a cause

[Many] believers in psi point to the ganzfeld experiments as proof of paranormal activity. They note that a .25 success rate is predicted by chance but Honorton had some success rates of .34. One defender of psi claims that the odds of getting 34% correct in these experiments was a million billion to one. That may be true but one is begging the question to ascribe the amazing statistic to paranormal powers. It could be evidence of psychic activity but there might be some other explanation as well. The amazing statistic doesn't prove what caused it. The fact that the experimenter is trying to find proof of psi isn't relevant. If someone else did the same experiment but claimed to be trying to find proof that angels, dark matter, or aliens were communicating directly to some minds, that would not be relevant to what was actually the cause of the amazing statistic.

The divine fallacy or the argument from incredulity is a type of argument to ignorance. If others can't disprove a claim, that is irrelevant to its truth. Arguments from ignorance put forth the irrelevant fact that something can't be done or proved, so some other claim must be true. The truth of any claim depends on the evidence in support of it; claims that the evidence doesn't prove a claim is true is irrelevant to whether some other claim is true.

Science hasn't disproved the possibility of miracles, or of God acting in the world. Science by definition is addressing the normal course of events; and miracles are, again, practically by definition, not the normal course of events.

And by the way, I happen to know that miracles occur, because I've seen them.

A cogent argument doesn't distort evidence nor does it exaggerate or undervalue the strength of specific data. The straw man fallacy violates the principle of fairness. In a straw man argument, one attacks a distorted version of another person's argument. Anyone using a straw man argument is refuting a position of his own creation, not the position of someone else. The refutation, however, may appear to be a good one to someone unfamiliar with the original argument.

A fifth quality of cogent reasoning is clarity. Some fallacies are due to ambiguity, such as the fallacy of equivocation: shifting the meaning of a key expression in an argument. For example, the following argument uses 'accident' first in the sense of 'not created' and then in the sense of 'chance event.'



Since you don't believe you were created by a god then you must believe you are just an accident. Therefore, all your thoughts and actions are accidents, including your disbelief in any god.

Another causal fallacy argues from the fact that two variables are correlated, they are causally related. You need more evidence than a strong correlation to provide adequate evidence for causality.

Such-and-such a historical figure was an influential scientist and a Christian, so that shows how important Christianity was to the development of science.

So-and-so was an influential abolitionist and a Christian, which shows that Christianity was integral to abolition.

Today I was reading a new post over at one of my favorite blogs,, by Robert Todd Carroll. The post is on informal logical fallacies – what they are, various kinds of them, and several examples of the different kinds. I'm sure that anyone who's spent a while debating on the interwebs has heard various phrases bandied about like, etc. – all examples of informal logical fallacies. As I was reading the post, I thought back to some of the discussions/debates over my "Why Christianity is Bullshit" series, and it wasn't hard to think of several arguments frequently and repeatedly advanced by theists that are informal logical fallacies.So I thought what I'd do is comb through Carroll's excellent post, and draw out some examples from my own experience to illustrate just how reliant theism is on demonstrably fallacious arguments.First, Carroll primes us on what an informal fallacy is:In other words, an argument like theisbecause it follows proper form:This means thatthe premises are true, the conclusionfollow. The KCA doesn't commit any formal fallacies, but it commits several informal fallacies (more on this later). This means that even though it's, it's. In order for the argument to be, the premises have to be true – and that means being free of informal fallacies.Having established the definitions, Carroll goes on to list several informal fallacies and provide examples, some of which are theistic. But as I was reading his list, I thought of several that I've heard that easily fit the descriptions. There are more in his post, and I highly recommend giving it a read; but I wanted to pick a few that stood out to me.This is when the arguer assumes what they are trying to prove. Carroll gives an example with the ganzfeld experiments:If this type of reasoning sounds familiar, that's because theists use it all the time – such as when arguing for a "design" to the universe, or arguing for miracles. Intelligent Design advocates assert that certain things are so improbable that there cannot be a natural cause; it must be a designer. But even if the ID advocates are right in the their estimations of probability (that's a whole other can of worms), an event being highly improbable does not prove that it was the result of an intelligent mind. Similarly, many who claim to have witnessed miracles claim that certain events, such a seemingly miraculous recovery from illness, are too improbable to be "natural". But highly improbable eventshappen – and there may be other mitigating factors (such as misdiagnosis) that can account for the alleged "miracle".This argument extends to the "privileged planet" argument as well, which claims that the conditions of Earth being precisely suited to support life are so improbable that they must be the result of a God. But again, even if theists were correct on the probabilities (they commit another informal fallacy, called the lottery fallacy ) demonstrated that God did it; it could simply be a highly improbable event.Carroll expounds:In my posts in theseries, one commenter objected to my argument that the available evidence does not support, and is in some cases flatly in conflict with, the evidence needed to demonstrate that certain Biblical stories – such as the Exodus – are historical. He accused me of making an "argument from silence" (which isn't actually a fallacy, nor was it my actual argument), and made a litany of excuses as to why the evidence could be obscure or non-existent. In other words, he was retreating to the argument that I had not conclusivelythe Exodus (and other Biblical events). And of course, I never claimed to do so. The fact that such events cannot be disproved is not evidence that they happened.This fallacy pops up in miracle arguments as well; since the evidence for miracles is pretty much always anecdotal and hearsay, and since miracles by definition can't be repeated as would a scientific experiment, it's often claimed that we skeptics can't prove that miraculous events didn't happen. In his debate with Sean Carroll and Michael Shermer , Ian Hutchinson literally made that argument, saying,He later adds,Checkmate, atheists! Please. These types of arguments are impotent. The inability to disprove miracles does not help one iota to establish that they happen; and one runs into an epistemic minefield when claiming that there is an empirically undetectable force or agent that nonetheless influences the natural world.One of my biggest complaints about the bookis that it argued against caricatures of atheist arguments, rather than addressing what we actually believe. Carroll explains:Several examples come to mind. It's often falsely argued by theists that atheism requires the non-believer to assume that materialism is true , or that atheists believe that they can disprove the existence of God or the supernatural. But it's perhaps most prevalent in the oft-repeated lie that atheists think that believers are dumb, uneducated, or whatever else (insert your pejorative) – you can be smart, and right and rational about many or even most things, and still hold beliefs that are erroneous or even delusional.Carroll:Equivocation is the undoing of the infamous Kalam Cosmological Argument ; in the first premise, it uses the term "cause" in the sense to which we are accustomed – the cause-and-effect of Newtonian physics – and then, in the conclusion, takes it to mean some sort of speculative "supernatural" or "non-physical" causality. It similarly confuses the concept of "beginning", which we generally take to mean as an event within time, and asserts that the universe"began", which would require some kind of speculative "non-physical time" (in case you think I'm making that up, William Lane Craig defends the concept of non-physical time here ).I've also heard theists frequently equivocate regarding the meaning of "faith". Sometimes it's that extra "leap" of believing something even if the empirical evidence doesn't get you all the way there; sometimes it's in the sense of "trust" or "hope"; still other times, it's in the sense of "assumption". It just depends on where in the argument the theist is using the word.This is a fallacy of insufficient evidence, as Carroll explains:I've heard a litany of arguments like this:Isaac Newton was a profoundly influential scientist and a Christian. But does that mean that Newton could not have (or would not have) discovered the laws of motion, optics, and universal gravitation were he a Dawkins-esque atheist? Of course not. People accomplish great things in various fields of science regardless of their religious views, because there is no necessary connection between the two. And while it's true that many Christians opposed slavery, it's also true that many Christians – for many centuries – supported and participated in slavery.There is quite a bit more in Carroll's post, so I highly recommend checking it out here