Moving on from the relationship of meaning to experience, let us now start to consider the relationship of belief to experience. A mere signification about experience begins to become a belief when it involves theory: the positing of a representation of the world we believe exists, or at least of the one we coherently encounter. By ‘theory’ here, I mean quite a wide band of beliefs, from the most general (say, the theory of gravity) to the specific (there is a rose outside my window). I am also encompassing what scientists would call a ‘hypothesis’ when it is more provisional, or what they would misleadingly call a ‘law’ when it is less provisional. Even the most specific of theories involves a degree of generalisation: to conclude that there is a rose I put together my experiences over more than one instant, and of more than one feature of the flower (I have to put together the size, the colour, the shape and distribution of petals etc, to conclude it is a rose). To draw specific conclusions I am also often making comparisons with other objects to enable me to classify new ones. We really can’t avoid a degree of generalisation, and hence of theory, whatever we assert.

I cannot justify my claim that an object is a rose only from my experience at one instant, because a lot more is assumed than my experience at one instant. If I were to put together my experiences of similar flowers on a number of occasions and generalise (“I will call this thing a rose”) I would have a degree of justification depending on the number of occasions, but subject to uncertainties of memory and of the correct identification of the flower. In practice, with many such everyday objects, I have been taught to identify a rose since childhood and depend on other people’s labelling, identification, and indeed cultivation of roses. The degree of uncertainty that comes from others’ testimony here has to be balanced against the amount of experience from others that is being drawn on, which in this case seems to make it overwhelmingly likely that my belief that there is a rose outside my window is correct.

In this approach I am following Hume’s view that verificatory experiences give no certainty to a theory, but that they do add incrementally to its probability – a probability that needs to be understood psychologically. However, I do not agree with Hume that we have no control over this process (Hume was a determinist or ‘involuntarist’ about beliefs). We are not forced by further experiences to believe the theory that they support, because we are capable of changing the theory to fit our prior assumptions, and even changing our interpretation of the implications of past experiences when we change our theory. Probability is not a kind of score-card kept by the gods, who reward us with total belief when we have totted up enough confirmatory experiences. On the contrary, it is our own attempt to measure incremental justification, and just as fallible as any other judgement.

To make our assessments of probability as reliable as possible, it is not only the number of confirmatory experiences and testimonies that need to be taken into account, but also the degree of adequacy of those experiences (and of the experiences that support the testimonies). The amount of evidence is one factor, but the quality of evidence is another, and may outweigh the quantity. If the evidence is likely to be affected by metaphysical assumptions, this is a major point against it, making it more likely that evidence will have been selected or interpreted prejudicially to fit the theory – or to not fit the theory in the case of negative metaphysical assumptions. For example, on the subject of religious experience, by far the most useful evidence comes from those who approach the subject neither with the assumption that God speaks through it, nor with the opposing assumption that it can be reduced to a material explanation.

In empirical investigations, it is common to take credibility criteria into account where other people are concerned – which may involve roughly estimating the adequacy of their experience. For example, do they have a vested interest? Do they have relevant expertise or direct experience to offer? However, we do not usually apply credibility criteria to ourselves. To consider the justification of our use of experience to support theory, this is exactly what we need to do – that is, not just assess the strength and coherence of the evidence available to us, but our chances of being wrong about it. For more detailed discussion of the implications of this, see section 5.

The complexity of the response that we need to experiences that confirm a theory is given a further twist when we come to disconfirmatory experiences. We can no more prove that an experience falsifies a theory than that it confirms it, even though a falsification, once accepted, is much more decisive than a verification, as it means that the theory if wrong. If my theory is that all Scotsmen like porridge, I only have to find one Scotsman who does not to explode the theory. But is he really a Scotsman? His grandmother was English, after all. And does he really not like it? He might just be lying due to a complex about his Scottish identity, but secretly eating porridge in private. The scope for ad hoc modification of the theory or re-interpretation of the evidence is still great.

Popper’s requirement for criteria of falsifiability stipulated in advance will go a long way towards freeing a theory from ad hoc manipulation. But (applying linguistic scepticism again) no such criteria are ever going to be completely free of possible category disputes and ambiguities. In the end it is recognising the falsifiability of the theory (an aspect of its provisionality) that increases the adequacy of our use of experience in supporting it. This recognition is a psychological criterion rather than the purely rational one that Popper hoped to find. Because there are no definable rules that we can apply with certainty to determine whether falsification has occurred, we are reliant on relative judgement. It is thus the objectivity of the right hemisphere and its integration of judgement, rather than the left hemisphere’s quest for certainty, that will provide the crucial final move in justifying a theory.

Whilst the philosophy of science has much to contribute to an understanding of the ways in which experience can justify theory, there is one tradition of scientific method that appears to rest only on dogmatic foundations and so must be dispensed with in Middle Way Philosophy. This is the tradition of an absolute requirement for public observability. The public observability and/or reproducibility of the evidence for a theory makes it scientific according to the conventions of science, but it is only one factor contributing to judgements about the justification of theories for individuals. Some theories held by individuals may only be about privately observable matters, but this does not disqualify them from being the subject of theory. In some such cases, the adequacy of the experiences that support a theory may be much more important than the fact that they are publicly observable. This is particularly the case with meditation, where records of individual experience may provide a lot more justification for theoretical conclusions than brain scanners – not because brain scanners are not informative at all, but because ‘internal’ experience is the main focus of meditation and the main source of evidence about it. So, the public observability of evidence forms only one non-essential element of the way we can use experience to justify theory. The quantity of evidence forms another aspect of this justification in finding a theory increasingly probable, but the adequacy of the experiences that provide evidence for it are the most important element. I shall be returning to these points and developing them in more detail in my account of justification in section 5.