I may start a series addressing some popular forms of atheistic arguments because, like it or not, you’ll run into them frequently. This is due to the popularity of guys like Richard Dawkins, Bill Maher, random Youtube atheists, etc. These arguments are not exactly philosophically sophisticated, nor are they used by all atheists, but it is nonetheless helpful to discuss why they are mistaken and even flat naive sometimes. In any case, I’ll start with the “You can’t prove a negative” complaint by many atheists.
Often, when one asks an atheist to present positive arguments for his worldview, he resorts to saying that proving a negative is impossible. In other words, it is allegedly unreasonable to expect a positive case for atheism because it is not possible, in principle, to prove that God does not exist (a negative statement). Because it is the theist who posits the existence of God, he is the one who has to present positive arguments while all the atheist must do is refute the arguments given by the theist. There are a couple of reasons for this. One, it is normally easier to refute a position rather than build a positive case for a position, and therefore it is advantageous, from a debating perspective, to avoid the burden of proof and place it on the opposition. Second, it gives the impression that atheism is the default, rational position that one must take. Many atheists think that this suffices to place the burden of proof squarely on theists while they can happily avoid giving positive reasons for their own worldview. Atheists may also attempt to tell people to refute the existence of obviously absurd things like the Flying Spaghetti Monster to try to show that it’s an unreasonable thing to ask.
Though extremely popular, this sentiment is rather quite silly. It is absolutely possible to prove a negative; in fact, we do it all the time. Assuming any reasonable definition of “proof,” we can prove something does not exist either inductively or deductively. For example, people do not disbelieve in Santa Claus merely because there is a lack of evidence for his existence. They disbelieve in him because there is evidence against his existence, such as the fact that the person who ate the cookies in your living room and gave you presents was unmistakably your parents and not Santa Claus (among others). Now, since conclusions from this type of evidence would be arrived at inductively, it would not be considered an absolute proof against things like Santa Claus, but it would nonetheless be considered rational to hold and irrational to reject. Stronger proofs against the existence of entities would be concluded from deduction (where the conclusions are necessitated by the rules of logic if the premises are true), and while that is typically more difficult, there are many examples of this as well. For instance, we know that there is no such thing as a round square or a married bachelor because those are logically contradictory notions. Again, we do not disbelieve in the existence of round squares simply because there is a lack of good arguments for their existence, but rather we disbelieve in them because it can be logically shown that they cannot exist.
What is particularly amusing about atheists who duck their responsibility to make a positive case for their worldview is that atheist philosophers have long given both inductive and deductive arguments against the existence of God, quite clearly showing that it is possible, in principle, to prove the non-existence of something. A deductive example would be the logical problem of evil, where the existence of evil is said to be logically incompatible with the existence of God. With the dismantling of that argument by Alvin Plantinga, atheists have tried their hand with inductive arguments from evil, concluding that while God may not be strictly logically incompatible with evil, his existence is unreasonable to believe in given the evil that we see. Of course, I do not think these arguments have been successful, but that’s because they ultimately weren’t good arguments, not because it is principally impossible to prove a negative.
Atheism is in fact not the default position many of its adherents want it to be because it makes a claim on reality, namely that God does not exist and nature is all that there is (I’m assuming atheists are naturalists, which is fairly standard for our time). It is actually naive to believe in some perfect, neutral objectivity, but the closest thing to a “neutral” position would be a strong form of agnosticism, not atheism. And I mean true agnosticism, the kind where one does not make conclusions and is ever open to new arguments and evidence. Many atheists try to collapse the definitions of atheism and agnosticism in order to avoid the burden of presenting their own case, but this is either disingenuous because they’re purposefully equating two distinct positions or confused because they do not understand the distinction. Atheists are not merely shrugging their shoulders about the issue of God and the supernatural; they are positively claiming that it is irrational to believe in God and that nature is all that there is.
In fairness to atheists, some theists have tried to use this same saying in a fallacious manner in order to avoid hard thinking. They’ll tell atheists, “You can’t prove a negative, and therefore you can’t prove God doesn’t exist!” and think that’s a good enough reason to have faith. This is a mistake (so don’t do it!). Still, in my experience, this is not nearly as common as atheists who try to use this little bit of fake wisdom to absolve themselves of the burden of showing why exactly their naturalism is true.