It is commonly observed that we live in an increasingly polarised world. Strikingly, we are polarised not only about political issues but also about scientific issues that have political implications such as climate change. This raises two questions. First, why are we so polarised over these issues? Second, does this mean our views about these issues are all equally ir/rational? In this chapter I explore both questions. Specifically, I draw on the literature on ideologically motivated reasoning to develop an answer to the first question. Put briefly, we exhibit “directional biases” in our information-processing: we try to assimilate new information into our existing webs of beliefs. This means that those who are predisposed to accept the ca...