I've heard some people say that there are many paths, but they all lead up the same spiritual mountain. But, to me, it seems more like there are many mountains, or spiritual/religious traditions, and many paths up those different mountains. But the paths have differences and the mountains have differences. Only in the most general terms does it seem that all religions are "one". But all of them a progression like different grades in school? I don't see that. People and their religious ideas progressing? Yes, I'd agree with that. But only because old religions don't make sense, not because they are a "progression" leading to the next.
Wildly inaccurate interpretation of Christianity's purpose. Christianity is first and foremost about worship of Jesus/God, secularism takes a distant or even nonexistent role. You are, I presume, taking your opinion from secular 'rationalizers' who aren't part of the religion.
Sorry. For limited time, I reply to both at the same time.
Every religion had same type of goals. Generally speaking, the goal of each religion may be divided in to Two: 1) creating a new man in a spiritual sense. 2) bringing order to the society.
The first goal means, bringing teachings that cause human to aquire spiritual qualities such as 'forgiveness', 'kindness', 'fairness', 'generosity', 'patience'...etc.
The second goal means, by bringing a new set of Laws (Shariah), the religion brings 'order' to society. For example by punishing thieves, adulterers, murderers and bringing and enforcing laws of marriage and others, it brings an order to a society that was in 'chaos'.
However, each religion in order to establish the two goals had to bring different 'formula'. Think of it as a sick person. As each time the disease and conditions of the person changes a different 'medicine' with a new formula is needed. Likewise, as humanity in different ages, have different conditions, and problems, with a different level of maturity and capacity, therefore each religion has teachings perfectly formulated for the humanity of its own 'Age'. Therefore Jesus said 'I am the way'. In His time, His way, was the way to the truth. His way, was the way to salvation. His way was the way to save mankind from disease of jealousy, envy, selfishness...etc. In this age, however, Baha'u'llah's way is the way to the truth and to get mankind to the 'two goals'. It is His way, to bring peace and order to the earth. It is His way, to bring salvation and save mankind from the disease of their heart, from the superstitions, materialism, fanaticism, disunity... and etc. The reason is, Baha'u'llah's teachings ate perfectly formulated to cure the problems of our Age. Jesus formulated a perfect medicine (a set of teachings) for His time. It is like 10 years ago a man had kidney problem. The doctor gave him a set of medicine specifically formulated to cure the kidney problem. Now this year, he has heart disease. Can he use the same medicine as 10 years ago? or does he need a new medicine specifically for the new condition? Then how can we expect that the medicine that Jesus or Moses, or Muhammad, or Buddha gave for their own time thousands of years ago still work for our new age, when the fact IS, this new age, has its own conditions? Which part of this is difficult to understand?