Yes, Dostoevsky said it!

If you visit Christiaan Strange's Dostoevsky webpage, you will find the following curious pair of sentences:

IF GOD DOES NOT EXIST, THEN EVERYTHING IS PERMITTED.
OK... no matter how much the above statement sounds like him, and no matter how many times it has been attributed to him, it is beginning to look like it wasn't Dostoevsky who wrote this.

The webpage author adds:

We're going to keep it here for now (cause we like it) but if some wise soul out there knows from where this quote truly originates, please don't keep us all in suspense!

I sent an email addressing this question to the indicated address on the 30th of August, but nothing's changed, and I never received a reply. So, I'm going to copy what I wrote below.

My email:

On your webpage, you have the quote,

If God does not exist, then everything is permitted.

You add, it's beginning to look like it wasn't Dostoevsky who wrote this.

I'm sure there are a lot of people who would like to think so. Nevertheless, the quote does appear in The Brothers Karamazov. The two phrases do not appear together, but it is entirely consistent with the passage to put them together. Mitya is complaining to Alyosha about Ivan and Rakitin:

But what will become of men then... without God and immortal life? All things are lawful then, they can do what they like? ...

What if He doesn't exist? What if Rakitin's right -- that it's an idea made up by men? ... Ivan has no God. ...I said to him, 'Then everything is lawful, if it is so?' He frowned. 'Fyodor Pavlovitch, our papa,' he said, 'was a pig, but his ideas were right enough.' That was what he dropped. That was all he said. That was going one better than Rakitin.
— pt. IV, bk. XI (Ivan), ch. 4 (A Hymn and a Secret)
online: scroll about halfway down the linked webpage

Mitya protests to Alyosha that the non-existence of God implies that everything is lawful.

I have found the same quote numerous times on Italian websites (Se Dio non esiste, tutto è permesso, at www.karamazov.it). Apparently Sartre also considered it to be a quote, in French though. Unfortunately, I can't find an Italian translation online, and I don't have one handy.

It seems to be quite fair to say that Dostoevsky did indeed write it then, although not as one piece.

The entire passage bears reading. We can argue all we want about what Dostoevsky meant by the passage, but there's no doubt that he wrote those words, and he meant them as an argument. I happen to believe that they were also his own argument, since in that passage Dostoevsky also dismisses the notion of secularism. Unless, that is, you think that Mitya's thoughts aren't Dostoevsky's own:

Rakitin says that one can love humanity without God. Well, only a snivelling idiot can maintain that. I can't understand it. Life's easy for Rakitin. 'You'd better think about the extension of civic rights, or even of keeping down the price of meat. You will show your love for humanity more simply and directly by that, than by philosophy.' I answered him, 'Well, but you, without a God, are more likely to raise the price of meat, if it suits you, and make a rouble on every copeck.'

It's probably worth noting, in conclusion, that Mitya is on the verge of being condemned for the murder of his father, a crime which he did not commit.