Vermes: "thank God for stopping the Diatessaron"

This little quip in an essay on methodology for Jesus research from the late Géza Vermes made me chuckle to myself:

...the multiplicity of the Gospels has turned out to be a blessing, and we must thank God for stopping the Diatessaron of Tatian from replacing the individual Gospels. The variations in Jesus’ sayings as preserved in the three Synoptics and occasionally in John enable us to compare and evaluate the contradictions between them and in doing so select the essential boundaries of genuineness.
— "Reflections on Improving Methodology in Jesus Research," 23-24, in Jesus Research: New Methodologies and Perceptions edited by Charlesworth and Rhea

Indeed, Jesus research would have been quite difficult if all we had was the Diatessaron, though I can think of quite a few people that I've met over the years who seem to wish we had only one Gospel!