A Treatise of Human Nature · Chapter
Section IV: Of the Component Parts of Our Reasonings Concerning Cause and Effect explained
Hume argues that all reasoning about causes and effects must ultimately rest on impressions from memory or senses.
What happens
Hume argues that all reasoning about causes and effects must ultimately rest on impressions from memory or senses. He illustrates this with the example of historical belief, such as the assassination of Caesar, showing that chains of inference must terminate in some present impression or memory, otherwise they are chimerical. He also addresses the objection that we can reason without recalling original impressions, noting that the conviction may persist even if the impressions are forgotten.
Themes in this chapter
Empiricism and the Primacy of Impressions
Hume emphasizes that all causal reasoning must be grounded in impressions from memory or senses, otherwise it lacks foundation.
Skepticism About the External World
The section implies that without impressions, our reasoning about causes and effects is chimerical, highlighting the limits of knowledge.
Characters to notice
- David Hume
Author of the section, presenting his theory of causal reasoning.
- Julius Caesar
Used as an example of historical belief based on testimony and impressions.
Key passages
“Though the mind in its reasonings from causes or effects carries its view beyond those objects, which it sees or remembers, it must never lose sight of them entirely, nor reason merely upon its own ideas, without some mixture of impressions, or at least of ideas of the memory, which are equivalent to impressions.”
Even when we reason about causes and effects, we must always base our reasoning on something we have seen or remembered, not just on abstract ideas.
Hume establishes the necessity of impressions in causal reasoning.
“It is impossible for us to carry on our inferences in infinitum ; and the only thing, that can stop them, is an impression of the memory or senses, beyond which there is no room for doubt or enquiry.”
We cannot keep making inferences forever; eventually we must reach something we directly perceive or remember, which ends the chain of reasoning.
Hume argues that all causal chains must terminate in an impression.
“Thus we believe that Caesar was killed in the senate-house on the ides of March ; and that because this fact is established on the unanimous testimony of historians, who agree to assign this precise time and place to that event.”
For example, we believe Caesar was assassinated on the Ides of March because historians unanimously report it.
Hume uses historical testimony to illustrate how beliefs are grounded in impressions.
“Every link of the chain would in that case hang upon another; but there would not be anything fixed to one end of it, capable of sustaining the whole; and consequently there would be no belief nor evidence.”
If there were no initial impression, the entire chain of reasoning would be unsupported, leading to no belief or evidence.
Hume stresses the need for a foundational impression to support causal reasoning.