Unfortunately, I can't remember where I've read the following rule, but it went something like: Don't use "like" in place of "as". "Like" governs pronouns and nouns. "As" governs phrases and clauses. Is this true? If so, does that mean the below is wrong: His head was as strong as a hammer. And instead, it should be: His head was strong like a hammer. Because "hammer" is a noun and not a phrase or clause? I could use some clarification on this. Thanks very much.
I don't know any grammatical rules governing this, but to me the two sentences have subtle difference in meaning and aren't freely interchangeable, but both correct in their own way. "His head was as strong as a hammer." places his head on a measurement scale of strength values, with a value directly comparable to that of a hammer. His head is likely made of cast iron or stainless steel. "His head was strong like a hammer." is more of a poetic simile, not to be regarded as scientificly true, but to conjure up a sense of the type of strength his head has (in this case a physical robustness opposed to psychological discipline).
This is where ‘rules’ out of context cause problems. This rule applies to the fact that you should write: He looks like a tramp. (noun) He looks like him. (pronoun i.e. you indicate a tramp) He looks as if/as though he has been sleeping rough. (phrase) 'He looks like he has been sleeping rough' is incorrect grammar (even though, especially in American English, this has become common idiomatic use). But: When you write comparative sentences, or similes e.g. 'light as a feather', you put 'as + adjective + as + noun', and 'the same...as...' e.g. His head was as strong as a hammer, i.e. His head was the same strength as a hammer. His head was strong, like a hammer = The strength of his head resembled that of a hammer, but was not necessarily the same strength.
