The Components of Our Reasonings on Cause and Effectby David Hume
Causes Require an Immediate Perception or an Inference from an Impression
In its reasonings from causes or effects, the mind carries its view beyond those objects which it sees or remembers.
However, it must never lose sight of them entirely, nor reason merely on its own ideas, without:
- some mixture of impressions, or
- ideas of the memory equivalent to impressions.
When we infer effects from causes, we must establish the existence of these causes.
We have only two ways to do this.
By an immediate perception of our memory or senses, or By an inference from other causes, which causes again we must ascertain in the same way by:
- a present impression, or
- an inference from their causes, and so on, until we arrive at some object which we see or remember.
It is impossible for us to carry on our inferences to infinity.
Only an impression of the memory or senses can stop them.
Beyond this, there is no room for doubt or enquiry.
For example, we may choose any point of history and consider why we believe or reject it.
We believe that Caesar was killed in the senate-house on the ides of March because this fact is established on the unanimous testimony of historians. They agree to assign this precise time and place to that event. Here are certain characters and letters present to our memory or senses. We also remember these characters to have been used as the signs of certain ideas.
These ideas were in the minds immediately present at that action.
Those minds received the ideas directly from their existence or they were derived from the testimony of others.
That testimony was again derived from another testimony, until we arrive at those who were eyewitnesses of the event.
All this connection of causes and effects is founded at first on those characters or letters which are seen or remembered.
Without the authority of the memory or senses, our whole reasoning would be chimerical and baseless. Every link of the chain would in this case hang on another. But there would be nothing fixed to one end of it that can sustain the whole. Consequently, there would be no belief nor evidence. This is actually the case with all hypothetical arguments.
Hypothetical arguments do not have any present impression nor belief of a real existence in them.
Our present doctrine is that we can reason on our past conclusions or principles, without having recourse to those impressions that they first arose from.
Even if these impressions were erased from the memory, the conviction that they produced might still remain.
All reasonings on causes and effects are originally derived from some impression, in the same way that the assurance of a demonstration always comes from a comparison of ideas.
This assurance may continue after the comparison is forgotten.