by Jennie Ruby 
To be, or not to be, asked Hamlet, making those two infinitives among the most well-known phrases in English. An infinitive is a verb form with the word to in front of it, in the form to verb. To be, to think, to ski, and so on.
We use these verb forms as nouns, as adverbs, and as adjectives. But one thing is for sure: these verb forms are never used as the verb in a sentence, and therefore will never have a subject. That is why if the word who/m happens to be in front of an infinitive, it is not the subject of the infinitive.
Here are some problem sentences:
He wondered who/m to hire as the new ski instructor.
Jimmy asked who/m to ski behind.
They told us who/m to see to order the new equipment.
To determine whether to use who or whom, you try to figure out whether the word who is the subject of any verb. In all of these examples, the word who has a verb form immediately after it. But those verb forms are all infinitives. And since infinitives do not have subjects, the word who is not the subject of any of them. Since who is not the subject of any verb in these sentences, all of them should say whom:
He wondered whom to hire as the new ski instructor.
Jimmy asked whom to ski behind.
They told us whom to see to order the new equipment.
The whole infinitive thing is just one more reason who versus whom is one of the hardest parts of English grammar. Just remember–an infinitive never has a subject.
Are you an eLearning developer who has been tasked with creating an effective voiceover script? If so, consider attending my Writing Effective eLearning Voiceover Scripts class. I also teach the Writing Training Documents and eLearning Scripts class.
About the Author: Jennie Ruby is a veteran IconLogic trainer and author with titles such as "Editing with Word 2003 and Acrobat 7" and "Editing with MS Word 2007" to her credit. She is a publishing professional with more than 20 years of experience in writing, editing and desktop publishing.