Sapere aude!

Quote of the Day:

Dimidium facti qui coepit habet: sapere aude! - Horace

("He who has begun is half done: dare to know!").

I like both halves of this saying, but I have no idea how they fit together. Perhaps in this way: "The first step is the hardest; I encourage you to take that first step on the path to knowledge!".
"Sapere aude!" was apparently a motto of The Enlightenment, quoted by Immanuel Kant in his What is Enlightenment?

Source: http://en.wikipedia.org/wiki/Sapere_aude

Latin lesson for the general populace:

"aude!" means "be bold!, dare!, be brave!"; it is related to "audacious".

"sapere" means "to be wise, to know"; it is related to "Homo sapiens".

For more serious Latin buffs:

"dimidium": "half" - this is new vocab for me.

"qui coepit" - who [rel pronoun] has begun.

I don't understand this: "...facti...habet". "He has" + "done". First, why does "facti" end in "i"? (This contradicts my second point.) Second, this structure, if it is as it appears, using "have" + past participle to indicated the perfect present didn't appear for another 1000(?) years.

Aha! Maybe it means: "He has half of the deed who has begun."

Suggestions more than welcome.