Our decisions are often based on a combination of diverse factors such as sensory inputs, past actions, and estimates of value. There is increasing evidence that the brain does this via a simple operation: give each factor a weight, sum the results, use the sum to set the log odds of a coin, and flip the coin. This operation is called logistic classification. It is common in machine learning and economics, and has close cousins in psychology. I will illustrate this computation in multiple species, and will describe it in more detail in mice that perform an audiovisual decision task. Through large-scale recordings and localized inactivations, I will show how the log odds of a choice are progressively computed at key stages in visual cortex, auditory cortex, prefrontal cortex, and superior colliculus. The results point to a single view of how the brain makes a variety of decisions. It is optimal in certain conditions, but the brain uses it as a heuristic in a broader set of situations, by simply adjusting the weights as needed.