Introduction

Abstract

The power of the intellect to grasp concepts and truths intuitively that are neither derivable from sense perception, such as the concept of infinity, nor justifiable by empirical evidence, such as inviolable principles of ethics, has been widely considered a characteristic that sets humans apart from all other earthly creatures. Intuitive knowing is among the intellectual powers we have often ascribed to ourselves, a power first recognized in ancient Greek thought. Plato, Aristotle, and their scientific predecessors have operated on the assumption that “like is known only by like,” and consequently interpret our capacity to grasp general concepts, which admit (in theory) of an infinite number of instances, and to know ultimate truths, to involve a different “faculty” from that by which we sense or imagine the properties of ordinary objects. These ancient thinkers have observed that our apprehension of sensed properties of objects, such as their smell and shape, is shared by many animals that exhibit no evidence of the rational power of grasping the general concepts involved in the truth of an intelligible statement. Until recent times, the classical understanding of human rationality prevailed, but modern evolution is focusing its attention on the continuities between animal and human life, not the differences. The scope of human rationality, and the extent of our rational powers, has never been convincingly fixed. Indeed, whether we could do so is unclear, and the occurrence of intuitive knowing contributes to questions about our ability to establish these limits.