A Realist Theory of Science Roy Bhaskar

211 A Realist Theory of Science
knowledge that nature is stratified is secured a priori how can we
justify any particular piece of inductive reasoning? By giving grounds
for supposing that there is an explanation, located in the nature of
things (at the next highest rung of reality), for the generalization
claimed. It is the possibility of an adequate explanation, in terms of
real invariances, from which the behaviour concerned can, normically
understood, be deduced that must justify any piece of inductive
reasoning in science. Thus it is the possibility of the satisfaction of a
deductive criterion that justifies induction in science. But we know
that the world must be such that this is so. It is the structure of the
world that makes induction, when it is, a rational activity for men.
I have of course already argued that the conditions for inductive
scepticism only obtain if we deny the possibility of (β) above. If we
allow (β), i.e. a realist interpretation of the entities postulated in
scientific theory, then we do have a reason independent of the facts
identified at any one level of reality as to why one but not another
sequence of events must be forth-coming (if the system is closed).
Now as the argument for inductive scepticism turns on the alleged
impossibility of knowledge of necessary connections between matters
of fact and I have demonstrated how we can (and do) come to have
such knowledge a posteriori in science, it remains only for me to
examine the conditions of the plausibility of the traditional problem
of induction and to show how the galaxy of problems in its wake can
be rationally resolved.
The problem of induction arises if we restrict the grounds for a
generalization to its instances, i.e. if we accept Nicod’s criterion of
the evidence for a law. It is resolved in two steps: (α)* by allowing a
model of a generative mechanism or structure to supply the missing
reason that the coherence of scientific practice demands, and in
particular to provide a crucial part of the grounds for a law; and (β)*
by allowing that under certain conditions, i.e. if certain criteria are
satisfied, such models held out in the scientific imagination as
plausible representations of the real mechanisms of nature may come
to be established as real. Mechanisms are enduring; they are nothing
but the powers of things. Things, unlike events (which are changes in
them), persist. Their persistence does not need explaining. Space and
time are causally inert: they possess neither liabilities nor powers.
Now step (β)* involves experimentation. It is a condition of the
intelligibility of experimental activity that causal structures not only