Hi all! I have a question regarding the principal difference between QFT and string theory according to popular accounts. It is said that QFT deals with point particles leading to the well-known infinities in calculating the transition amplitudes whereas in string theory the interaction is smeared out and no infinities occur. I don't understand this argument: QFT is the quantum theory of fields whereas string theory is the quantum theory of strings. The world sheet has only two dimensions and seems to be more singular than a field, which extends in four dimensions. So there would be less reason for infinities to occur in QFT than in string theory according to this argument. How can we talk about point particles in QFT anyway when it is a quantum theory of fields?