i think both of them want the island to be protected but they have different ideas to protect the island, jacob thinks there should be people there on the island that is why he brought the black rock and 816 to the island, but esau(jacobs nemisis) wants the opposite he thinks inorder for the island to be protected there needs to be less people. like when shannon sees walt(esau) she runs into the jungle to find him then anna luca shoots her, esau planned that and when ben shot john, walt(esau) was there to help him and when john got out of the dharma pit he shot the girl from the freighter. This is all of esau's attempts to save the island. I also think that the one time that john and ben went in the cabin to see jacob and everything was shaking, it wasnt jacob. it was Esau. when it showed the fram of him sitting in the chair i looked at it fer a bit then shortly after that i saw Esau. their hair lines are extremly close and his nose is kinda the same shape.