Mistake x AS y, or mistake x FOR y?

Question

• Don't mistake my confidence for arrogance

• Don't mistake my confidence as arrogance

Is "for" or "as" more appropriate in the sentence?

Answer 1

The following definition of for is now obsolete, but it survives in few expressions like this one.

So in your example mistake my confidence for arrogance and mistake my confidence as arrogance both equivalent in meaning. They mean the same thing. But mistake my confidence for arrogance is idiomatic.

_{Definition reference - Oxford English Dictionary (OED)}

Answer 2

The expression "mistake X for Y" takes "for". It is simply set like that as a phrasal verb.

http://www.oxfordlearnersdictionaries.com/definition/english/mistake-for

http://dictionary.cambridge.org/dictionary/english/mistake-sb-sth-for-sb-sth

To "mistake X for Y" means that you wrongly identified X (which is what the thing actually is) as Y (which is what the person thought X was).

http://dictionary.reference.com/browse/mistake?s=t (sense 3)

http://www.merriam-webster.com/dictionary/mistake (transitive verb sense 3)

However, you can use "as" to as part of the "misinterpret as" meaning.

I mistook your exam score as how well you were performing this semester.

http://www.thefreedictionary.com/mistake

Answer 3

Don't mistake my confidence for arrogance.

Don't mistake my confidence as arrogance.

I think there's no difference in meaning between these sentences. When you misunderstand or misjudge someone or something to be someone or something else, you can use either "as" or "for" after the verb "mistake," but the use of "for" is more common. Look at the following sentences:

I mistook her offer as a threat (Oxford).

He mistook my politeness for friendliness (The Free Dictionary).

I think "as" and "for" are interchangeable in these sentences.

The use of "for" is also more appropriate when you confuse someone or something with someone or something else, for example, he mistook me for your brother.