[LeGrande]

Based on your assumptions that your senses or your perception of them aren't deceiving you. Is there any other reason in your mind for the existence of external reality? Or, why is there an external reality in the first place?

No to the first question and there is no why to the second question. The really fascinating question though is how. Answering that question is my life's quest, the process of discovering reality and truth is my goal, that might make me a Taoist.

[dan1123]

there is no why to the second question.

There's no questioning your assumptions then.