Logic and Biology: Emotional inference and emotions in reasoning Ronald de Sousa University of Toronto Final Draft of a paper forthcoming in J. Adler and L. Rips, ed., Reasoning Studies of Human Information and its Foundations (CUP) The unrefined and sluggish mind of Homo Javanensis Could only treat of things concrete and present to the senses W.V. Quine Tropisms and transitions: some leading questions Before planning and reasoning, there were tropisms. Tropisms have functions and make use of information detected, but they don't, I assume, involve any actual reasoning. Somewhere along the course of evolution, and at some time in any one of us on the way from zygote to adult, some forms of detection became beliefs, and some tropisms turned into reasoned desires. And at some stage—perhaps, if Quine is right, with Homo Javanensis—we became adept at processing information, that yet fell short of the power to abstract and generalize. What selective pressures can we then suppose to have effected in our brains, since then, the innovations required to bring us the capacity for fully abstract and general reasoning? I take for granted that reasoning is something we do; that much or most of what we do is influenced by emotion; that psychology is interested in everything we do; and that psychology is a branch of biology. These breezy premises raise a number of questions. 1. What kind of connection might there be between biology and rationality?