What does Generations to come it may be will scarce believe that such a one as this ever in flesh and blood walked on this earth mean?

The phrase suggests that future generations may find it hard to believe that an extraordinary individual, who significantly impacted the world, actually existed in human form. It implies that the person's life and achievements are so remarkable that they may be seen as mythical or legendary rather than historical. This reflects the idea that profound figures can seem almost beyond reality due to their exceptional qualities or contributions. Ultimately, it underscores the lasting legacy such individuals leave behind.