Yes, you may think you are travelling 60 mph, but your speedometer may be faulty.

But you can be sure of the relationships: you connect pattern "60 mph" with pattern "you" with pattern "in" with pattern "your car" with pattern "hour" with pattern "one 24th" with pattern "duration" with pattern "sunset till sunset" with pattern "Earth" with pattern "rotating" with pattern "mile" with pattern "length" with pattern "speedometer" with pattern "claims about speedometers" with pattern "ideas about what speedometers do" and so on.

Now, just as dictionaries are circular until you go outside them, to, say the guesses you made about meaning from context etc. made as a child; so one may ask about the circularity in the above. According to Dr. Dick, certain laws apply to the process of comparing and matching two networks of pattern-connections (that he calls "explanations" or "models") to create a third network (explanation) projected as it were by the other two.

Those laws are from the law of non-contradiction.
So your speedometer MAY be wrong; but you can be sure of the law of non-contradiction, and sure of the connections you made between the patterns.

There is an alternative to guessing though; riding the "edge of the very wave of universe creation itself", having direct knowledge of creation as it happens.

-dolphin