Members of contemporary society are regularly confronted by claims in the public media about scientific discoveries that have important consequences for every level of life, from the global scale of planetary warming to local issues such as selecting “eco-friendly” lawn care products. Whatever the scope of the issue, the public is often faced with conflicting claims, each offering evidence to support their view. In order to disentangle competing views whether at the broad scale of public discussion of policy and regulation, or the local level of selecting a product to purchase, it is imperative that citizens develop habits of mind to critically evaluate and make decisions on such issues. Most arguments in life are not characterized by the rules of formal logic in order to determine the truth or falseness of a proposition. Rather, most are informal arguments that exhibit a more fluid exchange of ideas where those involved attempt to appeal to one another in a variety of ways to accept an idea that is being offered. In order to sustain the argument, the interlocutors must presume that the ideas put forward are sufficiently reasonable to continue the dialogue, at least for the time being. This presumption of reasonableness is important for sustaining the dialogue, but it is also temporary and can change as the dialogue proceeds. At the point where the presumption falters, an argument in the dialogue needs to be revised or the interaction will no longer progress. The presumption of the reasonableness of a premise is not built upon the formal property of truth, but rather an informal logic crafted through the dynamics of evidence, reasoning, and the social relations between participants. Arguments founded on the acceptability or defeasibility of scientific evidence rather than “truth” are characteristic of most exchanges regarding socioscientific issues whether at the level of public discourse or personal choice (Walton 2008). One of the goals of science education is to enable students to become “fluent speakers of science” (Lemke 1990), equipped to engage in thoughtful deliberation about scientific Res Sci Educ (2014) 44:903–926 DOI 10.1007/s11165-014-9407-0