Animalism and Dicephalus: The Psychological Disunity Solution
Philosophia April 7, 2026 DOI: 10.1007/s11406-026-00985-3 (opens in new tab)
Study at a glance
AI-extracted from the abstract| Characteristics | Theoretical or philosophical paper Peer reviewed |
|---|---|
| Topics | Philosophy of mind |
| Keywords | Indeterminacy philosophy Philosophy of science Philosophy of language Psychological science Idealization Epistemology Organism |
| Key points | Argues that the dicephalus objection to animalism is best answered by the psychological disunity solution: the Hensel twins constitute exactly one organism and one person with two functional brains and a highly disunified psychology, rather than being a borderline case or two overlapping organisms. |
Abstract
Abstract According to animalism, each of us is essentially a human organism. As such, the number of persons corresponds to the number of organisms. Dicephalic conjoined twins, such as the Hensel twins, challenge this view, as they appear to be two persons but only one organism. This is the dicephalus objection to animalism. In this paper, we address this problem. First, we introduce the Hensel case and outline the dicephalus objection (§1). We then discuss two prominent animalist responses: the indeterminacy solution, which holds that the Hensel twins are a borderline case of human animal (§2), and the overlap solution, which posits two overlapping organisms in the Hensel case (§3). We reject both views, arguing instead that there is exactly one organism and a single person with two functional brains (or psychological centers) and a highly disunified psychology. This is the psychological disunity solution (§4). We conclude by addressing potential objections to our view (§5).