What do you feel are the biggest obstacles to the reunion of Christians?

The biggest obstacle to reunion will be a lack of charity from all parties. As Saint Paul reminds us, “If we live by the truth and in love, we shall grow in all ways into Christ, who is the head by whom the whole body is fitted and joined together, every joint adding its own strength, for each separate part to work according to its function. So the body grows until it has built itself up, in love” (Eph. 4, 15-16). Charity, being an infused virtue, is only something that can be given by God. If all parties pray for each other and pray for greater charity, then the truth will eventually come out. It has taken hundreds of years so far, but there is no reason to believe that God will not succeed in bringing about unity for His “little flock” (cfr Lk 12, 32). We must, however, pray for it.