Coherentism - Difficulties For Coherentism

Difficulties For Coherentism

The main criticism facing coherentism, the isolation objection, is probably simplest to state from the point of view of someone who holds to the correspondence theory of truth. This states that there is no obvious way in which a coherent system relates to anything that might exist outside of it. So, it may be possible to construct a coherent theory of the world, which does not correspond to what actually occurs in the world. In other words, it appears to be entirely possible to develop a system that is entirely coherent and yet entirely untrue.

It is surprisingly difficult to even state the problem from the point of view of a coherentist, because the phrase correspond to reality has a different meaning in a coherentist system. For a coherentist, reality is exactly the entire coherent system. It is simply not possible for a coherent theory not to correspond to reality, if reality is the very same thing as the entire coherent system. However, coherentists need to account for propositions which report observations, such as: "I believe it is raining because I looked out of the window and saw it was raining".

Put another way, coherentists might reply to the critic that any substantial system that was not true would by definition contain some contradictions, and so be incoherent.

This should become clear by looking at the differences between a coherentist and correspondence account of a scientific advance. Newtonian mechanics was shown to be inconsistent with certain experiments, notably the Michelson-Morley experiment. The theory used by physicists was thereafter changed from Newtonian to relativistic mechanics.

One who held to a correspondence theory might say that there was an apparent lack of correspondence between the model (physics) and reality, and that the model was altered in order that it correspond to the observed facts.

A coherentist account might claim that before the Michelson-Morley experiment, physics formed a coherent theory. But then the experiment was performed. These experimental results form a part of the account, yet the results were inconsistent with the expectations of the accepted theory. Thus the account was shown to be less coherent. This inconsistency was resolved by the development of relativistic mechanics. In this case a coherentist would need to explain how special relativity is more coherent than both Newtonian mechanics and the Lorentz ether theory, which explanation would lead us on from simple inconsistency.

Any lack of correspondence of the theory with reality may eventually lead to a lack of coherence within the theory, and this leads to a modification of the theory to restore its coherence. There would be little or no practical difference between a coherentist account and a correspondence account of theory change.

Another problem coherentism has to face is the plurality objection. There is nothing within the definition of coherence which makes it impossible for two entirely different sets of beliefs to be internally coherent. Thus there might be several such sets. But if one supposes—in line with the principle of non-contradiction—that there can only be one complete set of truths, coherentism must provide a way to choose between these competing sets.

A number of philosophers have raised concerns over the link between intuitive notions of coherence that form the foundation of epistemic forms of coherentism and some formal results in Bayesian probability. This is an issue raised by Luc Bovens and Stephen Hartmann in the form of 'impossibility' results, and by Erik J. Olsson. Attempts have been made to construct a theoretical account of the coherentist intuition.