How firm are your values, your morals, or your political, spiritual or philosophical beliefs? All those questions and more will be put to the test in this friendship. You might end up feeling like your pal challenges you at a deep level.
You just won't take the same position as your friend on a lot of the bigger issues, and instead of appreciating your differences as complementary, you may view them as a threat to your own point of view. This, in turn, will lead you to try to prove your point in an overblown or just unnecessary way. You could learn from this person, if you try to show them that you respect your differences; but this will be easier said than done. This friendship holds the possibility of expanding your mental horizons through exposure to all the new ideas and unique philosophies that your buddy will bring to the table, but don't expect it to be easy for either of you to accept your differences.