It's possible to beat the Shadow Temple without the Lens of Truth, though it's probably a good idea to know your way around. This does make it a lot harder, though, because you can't see invisible enemies, longshot things, or solid ground. And when you get to Bongo Bongo, after shooting his two hands, it takes either luck or skill to shoot his eye. What I did was I waited until he began to charge at me, aimed upward between his hands with my bow, and shot the eye. Trust me though, it wasn't easy. When I first got there, I was so low on health that I had to go back to the graveyard and get some fairies (thank goodness I had Farore's Wind). Another difficult part is when you're in the large area with all the guillotine things, because some of the ground moves back and forth; you have to get it at exactly the right moment. I'm going to need to get the lens of truth now, because I'm going to the Spirit Temple, and it's required in order to even get there.