Pratchett said the popular television programme "breaks most of the laws of narrative". "On planet Earth it's generally taken for granted that it's a bad thing to introduce into a narrative some last-minute solution that was totally unexpected and unheralded … The unexpected, unadvertised solution which kisses it all better is known as a deus ex machina – literally, a god from the machine. And a god from the machine is what the Doctor now is," said Pratchett, a fan of the show since his school days. "A decent detective story provides you with enough tantalising information to allow you to make a stab at a solution before the famous detective struts his stuff in the library. Doctor Who replaces this with speed, fast talking, and what appears to be that wonderful element 'makeitupasyougalongeum'. I don't know about you, but I don't think I would dare try to jump-start a spaceship that looks like the Titanic by diving it into the atmosphere."
"Much has been written about the plausibility or otherwise of the Star Trek universe, but it is possible to imagine at least some of the concepts becoming real. But the sonic screwdriver? I don't think so. Doctor Who's science is pixel thin. I'm sorry about this, but I just don't think that you can instantly transport a whole hospital onto the moon without all of the windows blowing out. Oh! You use a force field, do you?! And there's the trouble; one sentence makes it all OK," he wrote. "I just wish that it was not classified as science fiction."
Despite all this, Pratchett admits that he can't stop watching the programme, which he described as "pure professionally-written entertainment, even if it helps sometimes if you leave your brain on a hook by the door". "I might shout at the screen again, but I will be watching on Saturday," he admitted. "After all, when you've had your moan you have to admit that it is very, very entertaining, with its heart in the right place, even if its head is often in orbit around Jupiter."