> Causal linkage just means that that event participated in causing this event. The sun being in the sky is causally linked to me believing it's day time, for example.

Great example! In Ptolemy's time "the sun being in the sky" would have meant that the sun was in a particular phase in its orbit around the Earth. Now we understand that the sun is not actually "in the sky" but it is a hundred million kilometres away. Our understanding of what it means for the sun to be "in the sky" will likely undergo several revolutions in the next 100,000 years.

Second, the actual facts are not causally linked to your belief. Your perception that the sun is in the sky is causally linked to your belief that it is daytime. If I am a schizophrenic and I hallucinate that the sun is in the sky even though it is night time then do I "know" that it is daytime?

All of this probably sounds overly pedantic but teasing apart the details is exactly what we're trying to do here :)