The Booby Traps make no sense
"Only the penetant man will pass" - does it have to be a man?
In any case, it's not enough to kneel, you have to do a couple of rolls in the exactly right direction at the exact right moment.
Once you do, somehow the really old, self-resetting mechanism knows someone has passed, and suddenly doesn't reset anymore. Uh, how? Why? Why let everyone through after ONE Indy-vidual figures out your traps?
Makes no sense. How would these super old traps reset themselves anyway for who knows how many decades or centuries? Why wouldn't the metal rust? How did they build and test these traps?
"Iehovah"
Why doesn't a history teacher and professor not know how to spell, and think it's spelled with 'J'? Huh?
Also, when you look at the view of the traps from below, where Indy almost falls through the "J" (no one else had this kind of close call? If it's this easy to have close calls and yet live, is it even dangerous?)..
..you can clearly see NOTHING holding up any of the letters, they just magically stay up. What?
If there WAS logically something holding up the RIGHT letters, then Indy could, while hanging down there, just look at where the path is, and walk there. No need to spell or jump clumsily, just walk through where he saw the supported letters were. Alternatively, just step with ONE foot on each letter and thus drop the ones that are not supported, so only the stable ones are left.
This trap makes no sense from any point of view I can figure. Just look at the viewpoint below Indy, when he almost falls.. how does that make sense? HOW?
"Leap of Faith"
This might be the most ridiculous thing of them all, and most nonsensical.
Light in ancient times was not easy to get. You either had to use very smoky and smelly oil, like fish oils, or candles that didn't provide much of it. The only bright light source was the 'daylight', but in a cave system like this, that would change constantly and drastically.
Would this bridge look the same on a cloudy weather? It would ONLY work at a VERY specific time of a day, at a VERY specific, sunny weather, and even then, it would be covered with dust, rocks, leaves, spider webs, you name it.
Ancient paint would most likely fade during all that time anyway, so it would still not look the same, and because your eyes show things in three dimensions, a 2D-painting would ONLY fool you if you look at it from a very specific, exact spot, one eye closed. Use both eyes and you easily see there's a bridge there.
This bridge somehow doesn't cast shadows or receive shadows?
I mean, you can find pictures of amazing trick art that is painted with a weird, forced perspective, which counters the actual perspective you see, so it looks very 3D and cool, but only through a camera lens. It doesn't work in real life, because you'd have to be at a very specific spot and close one eye and all that.
This bridge painting is basically a version of that, and ANY MOVEMENT would instantly reveal it, because a distant wall of a crevice would not seem to move much when you walk towards it, but a painting would seem to instantly move closer to you, because it's RIGHT THERE. This would change the perspective instantly..
There are SO many reasons why this bridge thing would NEVER, ever fool or convince ANYONE. There's absolutely NO WAY to paint a convincing wall not only in the proper counter-perspective back in the day, but also because the lighting is NOT constant, far from it, and it would always look fake no matter how well you paint it.
It's another movie trick that would never, ever work in real life, so Indy should not be fooled by it at all. All he has to do is look left or right, up or down, look at the bridge while walking towards or away from it, and so on.
Not that much of this movie makes sense when you think about it, although it is the best of the Indy movies.
They say that 'white torture' is psychologically really horrible. It's basically because you have no stimuli, everything is white.
This knight would have lived in almost as bad an isolation chamber without any entertainment for hundreds of years? It's not the 'getting older', but it's the 'how would he not become completely insane' kind of thing. What did he eat and drink? No matter how healthy you are, you are still going to get hungry and thirsty, and your body and organs can't function if they don't get nourishment or energy somewhere. Did this knight learn how to eat pure energy that he doesn't get much from the sun in a dark cave anyway?
How is there so much light in the cave, did this knight go to the market and buy modern oils and such to keep the flames lit?
Where did the knight get all the cups, and wouldn't they be worth something, being ridiculously old artifacts that this ARCHAEOLOGIST doesn't even glance twice?
Who devised this whole 'test'-thing anyway? I mean, it would've taken a long time and a lot of planning to create, just to wait for hundreds of years for some intruder to take the test?