But surely if Baha'u'llah was the current Manifestation of God, and the one for the thousand or so years after his death, come to establish a unified world, etc., he would know that there would in time be people who might want to see some evidence that he knew about regions of the world and religions and their teachers beyond those with which he had come into contact...Right?
Referring to Abdul-Baha (or Shoghi Effendi) doesn't really work in this instance, because Baha'u'llah's challenge was regarding his own knowledge.
Of course He has that knowledge but He won't say something that cannot be verified. What's the point of speaking about names of people who we have no record of? How would that prove He was any more knowledgeable as people could just say He made it all up?
I think what you can't challenge is His solution for today's problems.
I bet you can't find a better solution or imagine something higher or better than world unity or the oneness of mankind. There is no higher form of teaching for this age than what Baha'u'llah taught.
So much so that if you want to go into it in real depth I can show how countries all over the world are adopting the teachings of Baha'u'llah as cutting edge for today's problems.
From multiculturalism to interfaith to women's rights to human rights and religious tolerance these have had all their origins in specific verses and passages of Baha'u'llah.
Baha'u'llah said His Words were 'creative'. In other words what He says will happen or the means will arrive to make it happen.
Just one or two words of Baha'u'llah brought about the internet, world travel and world communications. Because His Words bring about the sciences to enable the Words to be fulfilled.
Imagine in 1860's Baha'u'llah saying the world is but one country and mankind its citizens and how people mocked Him as there was no such thing as one world or world communications or travel yet today look how science has 'obeyed' the Words of Baha'u'llah and brought about the fulfillment of 'everything' He has written.
And this goes on and on. The end is limitless.
From the moment Baha'u'llah declared men and women equal look at women's rights arising all over the world. Coincidence? Hardly.
Look at even the marriage law of one year separation by various governments. Almost word for word the same in His Book of Laws revealed around 1873.
What about the League of Nations, the UN, world bodies? Baha'u'llah called in the 1800's for a world assemblage of all the kings rulers and leaders of the world. They 'obeyed' Him and formed international bodies and the world continues to gravitate towards His laws and teachings regardless of whether they accept Him or not.
You and I are surrounded by the teachings of Baha'u'llah being implemented in our daily lives everywhere. And none is complaining until it comes to recognition. But His teachings are being adopted all over the planet because they are what is needed.
All the sciences and arts serve His Revelation Whose aim is the oneness of mankind. The purpose of it all is human happiness to put an end to war and improve the lives of people everywhere.
This is the age when humanity will attain to a golden age of peace after thousands of years of suffering.
There is no power on earth that can transform our world into a place of peace, harmony and happiness except the teachings of God for this age.