Facts and Negative Evidence

Facts are curious entities. They are commonly defined as either truth-makers or truth-bearers. As truth-makers they are states of affairs. As truth-bearers they are the abstract contents of beliefs (i.e., propositions).

A problem with the truth-maker view of facts is the existence of negative truths. If there always must be something that makes true that which is true, what are we to say when there is no entity in the world that makes a negative truth true? What entity “makes true” propositions like {There is no God} or {Carbon monoxide is an odorless gas}? What non-occurrence event of the existence of God makes it true that {There is no God}? Does the non-existence of the property of odor in carbon monoxide make true the proposition that {Carbon monoxide is an odorless gas}? How is lacking a property able to “make true” when the basic truth-maker principle requires there to exist at least one entity that necessitates the truth of that which it makes true? Is odorlessness an entity capable of such a task?  

This problem is relevant to the concept of evidence. The nonoccurence of events is said to provide negative evidence. Such evidence is used in inferential contexts to draw certain conclusions. Consider the Sherlock Holmes’ mystery Silver Blaze. At night someone stole the horse Silver Blaze from the stable where he was kept. A watch dog and two grooms also lived in the stable. The grooms said they heard nothing during the night. Consider the following propositions:

  • b: The dog is a watch dog that would bark if someone attempted to steal Silver Blaze, and this would wake the grooms and alert them of the intruder.
  • e: The dog did nothing during the night.
  • h: The person who stole Silver Blaze knew the dog well.

The probability of the hypothesis given the evidence and background information leads Holmes to conclude P(h|e & b) = High. The incident that allowed Holmes to conclude that h is likely was the non-occurrence of barking by the dog during the night. How does the state of affairs of non-barking (as an entity) make true (or probable) the hypothesis? If negative evidence is admissible as facts in the truth-maker sense where does this lead? Does the non-occurrence of my death (or bodily injury) while driving “make true” the proposition that {Driving is safe}? After all, the incident of non-occurrence of injury does increase the probability of the safety of driving. One problem is the scope of such commitments. Would all non-occurrence events equally “make true” propositions true? Inferentially speaking, would negative evidence, as “making true”, lead to the irrational assignment of probabilities in various hypotheses?

Imagine one dumps truth-maker theory and opts for truth-bearer theory instead. This has the upshot that propositions can be properly modeled and made to “obey” the rules of probability. Facts simply bear truth, they don’t make it. But, this leads one to wonder where the truth that propositions come to bear originates? If not in states of affairs, then is their truth a matter of mere stipulation? To be a fact is to be a true proposition. This can be stipulated as the intersection of the set of all propositions that exist in a world w and the set of all propositions that are true in w. But doesn’t the existence of physical evidence (or non-inferential evidence) tell against such a view? Why would one need to report on the evidence or duplicate the evidence in a that-clause when the evidence is before one’s eyes? This seems especially troubling when producing the evidence in court has greater probative value (e.g., think of O.J. trying on the leather glove during his trial) than a that-clause about the same evidence. If the claim is that all evidence must be rendered propositionally, then producing the evidence in court should not affect the probative value over and above the value when the evidence is propositionally presented. For instance, that {The glove doesn’t fit O.J.}, relative to certain background information, should have the same effect as O.J. trying on the glove in court and the jury seeing it doesn’t fit. Yet, perceptually viewing the material evidence in a state of affairs does seem to affect the probative value of the evidence.

For me, the jury is still out on a truth-maker versus a truth-bearer view of facts. Perhaps a hybrid view is possible. On such a view, facts might be rendered as either truth-makers or truth-bearers depending on the context of confirmation. Different contexts impose different standards of evidence.  For example, testimonial evidence carries different probative value depending on whether one is in the context of science or law. To this end, coming up with principles that guide the rendering of facts to various contexts of justification seems a worthwhile pursuit.

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