This Article explores the conceptions of responsible agency that informed legal analysis in nineteenth-century America. Standing behind the “reasonable man” famously drawn by Oliver Wendell Holmes, Jr., there was a second figure, which I call the “default legal person,” who personified mental attributes an individual needed to possess— at a minimum—in order to be deemed a legally accountable agent. This default legal person, I argue, was first articulated in the post-Revolutionary period by jurists drawing on new “enlightened” forms of Protestantism, and particularly on the Scottish Common Sense philosophy in which they were schooled, in order to delineate the mental prerequisites of legal responsibility. The figure they constructed was, in essence, a creature of Common Sense, one divinely endowed with intellect, free will, and moral sense.
Turning to the law reports published over the course of the century, and focusing more particularly on the little-studied civil side of the docket, we find that judges tended to deploy the default legal person in the same fashion across cases and time. In any instance in which a plea of incapacity was made, this legal figure served to set the threshold of mental competence—to illustrate how much “mind” a person needed for a particular civil act or wrong to be attributed to him. Yet this is not to say that the threshold of capacity was set at the same level in every doctrinal field. To the contrary, judges altered the character of the default legal person as they transposed it from one field of law to the next, suggesting as they did that the specific mental attributes one needed to be a competent legal actor differed, depending upon the nature of the act involved—whether it was a will, contract, deed, or tort. Across all doctrinal fields, however, judges faced a similar and perplexing problem: How could they determine whether a given individual actually lacked the capacity to act with feeling, intelligence, prudence, or malice? Was it sufficient to show that the act itself was eccentric, or was it necessary to demonstrate that the party in question suffered from some sort of mental disease, as defined by medical men?