It's important to note here that there are two versions of the speech, and the only place they differ is with the addition of new opening and closing lines. Basically, he had a version that he intended to deliver, and then version he actually delivered.

So in the "official" version, the one he intended to deliver, he opens right with the main idea, Europe is in trouble, along with that appeal to the audience's intelligence. It's a bit more streamlined in its structure, but it's a little sudden. Just gets right to the point and then leaves.

The version he actually gave added a few remarks about how honored Marshall was to be giving the speech. It was a polite way to start things rather than just barreling headlong into the main idea of the speech.

Want to see the difference for yourself? Check it out:

Written version:

I need not tell you gentlemen that the world situation is very serious. That must be apparent to all intelligent people. I think one difficulty is that the problem is one of such enormous complexity that the very mass of facts presented to the public by press and radio make it exceedingly difficult for the man in the street to reach a clear appraisement of the situation. Furthermore, the people of this country are distant from the troubled areas of the earth and it is hard for them to comprehend the plight and consequent reactions of the long-suffering peoples, and the effect of those reactions on their governments in connection with our efforts to promote peace in the world. (1.1-4)

Live version:

Mr. President, Dr. Conant, members of the board of overseers, ladies and gentlemen, I'm profoundly grateful and touched by the distinction and honor and great compliment accorded me by the authorities of Harvard this morning. I'm overwhelmed, as a matter of fact, and I'm rather fearful of my inability to maintain such a high rating as you've been generous enough to accord to me. In these historic and lovely surroundings, this perfect day, and this very wonderful assembly, it is a tremendously impressive thing to an individual in my position.