If you have not had the opportunity to watch this speech in its entirety, I encourage you to do so. Now be warned, some perhaps don't understand the impact of this speech because they didn't make it past the first half of the speech. You see, the most well-known part of the speech is the second half. Why is this so?
Like many great presenters, Dr. King was well prepared and had his manuscript laying before him during what would be the most important presentation of his life. He stayed true to that manuscript for the first half. He read those written words with the same verbal eloquence and hypnotic rhythm typical of his delivery style. But something was missing. The words he spoke in the first half of his presentation were no less important than the second half, but his usually present compassion and conviction felt somewhat muted.
Then, it happened. The change. What caused the second half of his speech to become so passionate and full of conviction that it would go down in history as the best speech of our time? Clarence B. Jones, speechwriter for Dr. King, explains in his book "Behind the Dream." You see, partway through the speech, a friend of Dr. King's yelled, "tell 'em about the dream!" Many didn't hear her make this exclamation, but he did. And the tides turned.
Dr. King left his manuscript behind and began to, as Jones described, take them to church. So, if you have not had the opportunity to watch King's speech in its entirety, I encourage you to do so. Not only is his message an important one that should never be forgotten, it should be shared. Additionally, if you want a good lesson in public speaking, watch and pay attention to when the shift happens and how it makes it inevitable that King inspire and invigorate the crowd.
As a speech teacher, it's my job to make sure my students understand the importance of preparation and practice. We talk a lot about "extemporaneous" speaking, where you prepare the speech in advance, practice it so you know it well, but deliver with little to no notes. It's much different from reading from a manuscript and the difference in impact is clearly evident in King's speech. King had delivered a version of the second half of his speech in a prior presentation, so it wasn't really made up on the spot. But because he put the manuscript to the side, looked up from his notes, recalled a message that he had previously prepared and delivered that message from the heart, he was able to take an entire nation's breath away and positively influence the march toward civil rights.