Hume

Locke’s Hesitation on Personal Identity:
- John Locke added a chapter on personal identity only in the second edition of An Essay Concerning Human Understanding.
- He never revisited the topic afterwards, suggesting he was uncertain or dissatisfied with his conclusions.
Hume’s Approach to Identity:
- Like Locke, David Hume approaches personal identity through a broader investigation of identity in general (e.g., ships, houses, churches, matter, and souls).
- Unlike Locke, Hume explicitly highlights human errors and mistaken beliefs regarding identity, especially personal identity.
Hume’s Empiricist Framework:
- As an empiricist, Hume argues that an idea is only legitimate or warranted if its source can be clearly accounted for.
- Hume’s project consists of two distinct phases:
1. Negative Project: Dismantling existing philosophical doctrines regarding a simple, persisting self.
2. Positive Project: Explaining how the human mind constructs the idea of identity despite experiencing only changing perceptions.

Hume targets philosophers who assert the existence of a persistent self, including René Descartes, Samuel Clarke, and Joseph Butler.
The Cartesian / Dogmatic Claim:
- Asserts that humans are continuously and intimately conscious of a "self" that is simple (indivisible), perfectly identical, and persisting continuously over time.
- Claims that certainty of this self requires no empirical proof or demonstration.

Hume rejects this traditional view, stating that we have no warranted or justifiable idea of such a self.

Failure of Sensory Impressions:
- We have no single, constant, or invariable sensory impression of a simple self.
- Logical Absurdity: The self is defined as the subject to which all impressions and ideas refer. Therefore, the self cannot be its own object of perception (analogous to how a camera cannot photograph its own lens in operation).
Failure of Pure Reason and Intellect:
- Philosophers like Descartes claim pure intellect grasps the self (e.g., the Cogito in Meditation II). Hume refutes this rationalist claim:
  - No Substratum Required: There is no logical necessity to posit an underlying substance or substratum to support floating perceptions.
  - Atomistic View of Mental Events: Particular perceptions (thoughts, sensations, emotions) are distinct, separable, and capable of existing independently.
  - Explaining Inherence: Claiming perceptions "belong to" or "adhere in" a simple substance fails to explain how they are connected.

When entering into what one calls "myself," one always stumbles upon a particular, fleeting perception (heat, cold, light, shade, pain, pleasure, love, hatred).
One never observes anything other than a perception.
Thus, introspection reveals only constant diversity and change, never a static, continuous self.

We perceive continuous change and diversity (e.g., due to blinking, head movements, or physical changes in objects).
However, we mistake this perceptual diversity for numerical identity over time.

To explain how the mind constructs identity, Hume identifies three key relations holding between successive perceptions:

Resemblance: Successive perceptions strongly resemble previous ones, causing the mind to overlook subtle differences.
Causation: Changes are perceived as natural, predictable causal outcomes of preceding states or functions.
Contiguity: Objects are perceived in spatial proximity or continuous spatial paths over time.

Identity is not grasped by sensory impressions or pure reason; it is produced by the Faculty of Imagination.
The relations of resemblance, causation, and contiguity allow the imagination to smoothly transition from one perception to the next.
This "smooth gliding" creates a distinct mental feeling that mimics the experience of a strictly unchanging object.

When applying this framework to the self, Hume notes that Contiguity must be dropped:
- Perceptions and mental states are non-spatial events; spatial proximity or location does not apply to thoughts or consciousness.
- Personal identity relies exclusively on Resemblance and Causation.

Memory serves as the essential engine driving the imagination in establishing personal identity:

Resemblance and Memory:
- Memory retains past impressions. The resemblance between present thoughts and remembered past thoughts enables the mind to link them into a continuous stream.
Causation and Memory:
- Memory allows us to perceive causal chains connecting disparate mental states (how one thought or passion gives rise to another).

Locke’s View: Personal identity extends only as far back as present consciousness and active memory can extend. Forgotten experiences are strictly excluded from personal identity.
Hume’s Revision:
- Memory does not merely produce identity—it also discovers causal relations.
- Once memory reveals that our mental events are bound by causal laws, we can logically extend our identity to periods, actions, and times that we have entirely forgotten.

Identity as a Psychological Fiction:
- Hume concludes that the identity ascribed to the human mind is a fiction constructed by the imagination.
- It provides no metaphysical guarantee of an immortal, indivisible, or substantial soul.
Explanatory Power:
- Rather than proving a metaphysical reality, Hume’s account provides a psychological explanation of how humans derive the practical illusion of a continuous self from a succession of fleeting perceptions.