Its a mix of both, your trading style could be an art, where as forex market is nothing without technology, which is a science....
It takes a little bit of knowledge to know precisely, or at least approximately if this or that will bring as much, it's about intelligence.I think it's both as some people said, if trading is just an art than it will be too risky and less likely to help you win a good amount of money, so in my opinion is a mix of both science and art, and science can be confusing as well.