In "The Secret of Father Brown" by G. K. Chesterton, Father Brown was saying that he prefers studying the murder from inside not outside:
I don’t try to get outside the man. I try to get inside the murderer. . . . Indeed it’s much more than that, don’t you see? I am inside a man. I am always inside a man, moving his arms and legs; but I wait till I know I am inside a murderer, thinking his thoughts, wrestling with his passions; till I have bent myself into the posture of his hunched and peering hatred; till I see the world with his bloodshot and squinting eyes, looking between the blinkers of his half-witted concentration; looking up the short and sharp perspective of a straight road to a pool of blood. Till I am really a murderer.”
Does "think" here mean "think about" his thoughts or "think by" his thoughts as we are the same person?
And what's meant by "hunched and peering hatred", as I never met such a posture with such a feeling?