sophistical

adj

1. Pertaining to a sophist or sophistry.
2. Fallacious, misleading or incorrect in logic or reasoning, especially intentionally.

   “This is, we believe, a fair summary of Mr. Lamb's doctrine. We are sure that we do not wish to represent him unfairly. […] But we must plainly say that his argument, though ingenious, is altogether sophistical.”

   “Assuming other people to be as sophistical as ourselves, and as intent as we upon winning the argument, they are likely to be no more honest than we.”