Quote from Automaton
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I guess that what I just said still doesn't imply the lack of an external world though, does it? It only implies that nothing can be known with 100% certainty about this external world.
Yep :)
Kant's Critique of Pure Reason is largely dedicated to trying to work out what we can know about things in themselves, ie. not just what we experience. It's a little bit weird and he makes big jumps similar to the idealism arguments, but the basic premise is the same as what you're saying: we can't experience the world itself but that absolutely does not mean the world itself is not there.