The correct statement is "I walk faster than John does." (or, possibly, "I walk faster than does John," but that's a whole other issue.) Comparisons have to be apples-to-apples; that is, the things you're comparing have to be similar or parallel. If you're comparing the way that you walk to the way that John walks, your sentence structure needs to make that clear. Otherwise, you could be comparing "faster" to "John." It's kind of hard to see how that could be in your example sentence, so let's take a different one:

I am more sensitive to criticism from Emma than Jenny.

This comparison is unclear; it could mean that I am more sensitive to criticism from Emma than to criticism from Jenny, or it could mean that I am more sensitive to criticism from Emma than Jenny is. We need to know which one it is, so we make that sentence either

I am more sensitive to criticism from Emma than from Jenny.

or

I am more sensitive to criticism from Emma than is Jenny.

Basically, your goal is always clarity, and if that requires one or more extra words to make a comparison explicit, then put those words in.

grockit_andrea wrote:The correct statement is "I walk faster than John does." (or, possibly, "I walk faster than does John," but that's a whole other issue.) Comparisons have to be apples-to-apples; that is, the things you're comparing have to be similar or parallel. If you're comparing the way that you walk to the way that John walks, your sentence structure needs to make that clear. Otherwise, you could be comparing "faster" to "John." It's kind of hard to see how that could be in your example sentence, so let's take a different one:

I am more sensitive to criticism from Emma than Jenny.

This comparison is unclear; it could mean that I am more sensitive to criticism from Emma than to criticism from Jenny, or it could mean that I am more sensitive to criticism from Emma than Jenny is. We need to know which one it is, so we make that sentence either

I am more sensitive to criticism from Emma than from Jenny.

or

I am more sensitive to criticism from Emma than is Jenny.

Basically, your goal is always clarity, and if that requires one or more extra words to make a comparison explicit, then put those words in.

Thanks for writing in Andrea; however in this sentence: I walk faster than John, isn't 2nd inference(faster being compared to John) an impossible inference ?
I think this sentence as written can facilitate only one inference-'I is being compared to John'

Let me know what your thougths are?

Good question!

You're right that the idea of comparing faster to John is illogical, but the sentence corrections don't take logic into account; whether or not you can infer the correct meaning, the comparison needs to be made explicit in order for the grammar to be correct.

Thanks for explaining Andrea. makes things little clear

grockit_andrea wrote:Good question!

You're right that the idea of comparing faster to John is illogical, but the sentence corrections don't take logic into account; whether or not you can infer the correct meaning, the comparison needs to be made explicit in order for the grammar to be correct.

Sure thanks Andrea.