Can someone please explain the bolded parts to me?

Question

The master said, with vehemence, "It's far above instinct; it's REASON, and many a man, privileged to be saved and go with you and me to a better world by right of its possession, has less of it *that this poor silly quadruped that's foreordained to perish;"* and then he laughed, and said: "Why, look at me—I'm a sarcasm! bless you, *with all my grand intelligence, the only thing I inferred was that the dog had gone mad and was destroying the child, *whereas but for the beast's intelligence—it's REASON, I tell you!—the child would have perished!"**

From A Dog's Tale by Mark Twain,

From what I understand many who have been privileged to possess REASON have less of it than a dog who is destined to be destroyed. am I correct? Does that mean than here? With all my great intelligence I could only infer that the dog went crazy and tried to destroy the baby. I don't understand the rest of the sentence " whereas but for..."

Answer 1

I don't know the work in question, but it looks like this is a very bad edition of it. I think you're right that the "that" should read "than". Taking out the confusing parenthetical section, it should read, "it's REASON, and many a man has less of it than this poor silly quadruped ... ". The part I've omitted says that humans can go to heaven because we have reason, unlike animals.

Then, in the second part, the speaker is making a contrast. With a slightly less convoluted structure, it might be rephrased, "With my intelligence, I inferred that the dog had gone mad and was destroying the child. Without the dog's intelligence, the child would have perished."

To explain that further: "whereas" is like "but": it makes a contrast between two statements. "But for" means "if it weren't for". I assume the situation is that the speaker thought the dog was attacking the child, and the dog is to be put down as a result, but the speaker now realises that the dog was quick-witted and saved the child from some unseen danger.

The missing piece now is, "it's REASON, I tell you!" This interjection makes a lot more sense to me if "it's" is "its" (i.e. the dog's). That way, we take it as: "the beast's intelligence—its REASON, I tell you!—" so he starts describing the dog's intelligence, and then goes on to say that it is more than intelligence.

Without starting a literary analysis, I'll just mention that he's speaking rhetorically: he starts by pointing out that reason is what separates man from the animals; then he compares the dog's intelligence to his own, as shown by its actions in saving the child; then he elevates the dog's intelligence to the status of reason.