Batman is the world's greatest detective because he has trained himself to instantly recognize and interpret even the most seemingly insignificant clue.
Example: a mad bomber has been plaguing Gotham City, randomly blowing things up. His latest attack has come in "the ghetto," and an injured Batman has gone down to investigate:
And there we witness the deductive brilliance of the Batman:
"Ghetto people don't own boats!"
Thank you, Bob Haney.
Why is Batman injured? Why the hell did the first caption refer to Easy Company? Because this is The Brave And The Bold Special (a.k.a. DC Special Series #8), (1978), which just may be the greatest comic book ever.
Proof? The 37-page story features Batman, Deadman, Sgt. Rock, and Sherlock Holmes (!) versus Lucifer--yes, the fallen angel Lucifer--and the ghosts of Guy Fawkes, Nero, Benedict Arnold, Bluebeard, Jack The Ripper, and Hitler. Plus, a group of evil Scottish nationalists (!) have stolen a statue of Batman from the Queen of England (!), and that bronze likeness functions as a voodoo doll to torture the Caped Crusader. And yeah, there's that mad bomber. Plus, Batman pays to dance with a hooker. Oh, yeah, and also has Easy Company versus the Loch Ness Monster.
Like I said, Greatest. Comic. Book. Ever.