Thanks to the International Quantum Year there is a lot of interest in quantum mechanics. While no one doubts its correctness, one often encounters the statement that quantum mechanics is counterintuitive and cannot be understood. My take on that has been unchanged since I first taught quantum mechanics. Reader warning: Strong opinion ahead.

People who express that quantum mechanics is counterintuitive and cannot be understood participate in a modern day version of the Copernican revolution, that is the shift from the Ptolemaic world view with Earth being in the center of the Universe to the Copernican world view with Earth being just another planet revolving around the Sun. Except they participate in this debate by supporting the wrong side. Just replace Earth by a classical world view that we consider normal and intuitive because this is what we experience as effectively classical beings. We naturally define everything in relation to that classical world view, therefore one it tempted to put that classical world view into the center of our mental universe. However, this is just another case of taking ourselves too seriously, of favoring a certain frame of reference because it is “ours”.

There is absolutely no reason why the laws of Nature should care about what we macroscopic beings consider normal and intuitive. So feel free to say that quantum mechanics is counterintuitive, but my recommendation would be to get over it and to move on.