As far as the difference in meaning between, Agree vs Agree with… There is none. For, in order to “Agree”, it is necessary to do it “With” another person, or an idea, opinion, philosophy, etc.. (All of which would come from another person.) Therefore — the only difference between the Verb: “Agree”, and the Prepositional Phrasal-Verb: “Agree With” — is in how these two are used.
When we use “Agree With”, there needs to be a Noun or Pronoun (acting as a Direct Object) directly after it in the sentence. This is usually a person, but can also be an: Idea, Opinion, Philosophy, etc.. To use “Agree” without the Direct Object, is usually as a statement in response to another, and the word “Agree” will be the last word in the sentence…
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