Taking Inference Seriously
I
am deeply honored to be here – to be virtually here – to receive
the Wigmore Lifetime Achievement Award.
There
is relatively little doubt that some of you associate my name with
the so-called (and now not so new) New Evidence Scholarship. The New
Evidence Scholarship began roughly in the late 1960s and early 1970s.
Mathematics and statistics have played a prominent role in the New
Evidence Scholarship, and a good deal (though by no means all) of the
new scholarship whose study I have promoted over the years makes use
of mathematics and statistics. The
underlying reason for my interest was never just the idea that
mathematical tools can shed light on the nature of evidence and
inference. I have always had a broader
and fuzzier goal, the goal of advancing the study of evidential
inference by employing a wide variety of conceptual tools and
branches of human knowledge, including but not limited to
mathematics, formal logic, and matters of that sort.
In
my own work I have used mathematical tools only sparingly, and
generally I have used only very simple mathematics (primarily
arithmetic and simple algebra). When I have used mathematical tools,
I have used them, in the main, not to construct models of the world
but, rather, to explore the nature of argument
from and about evidence. Mathematics
is, among other things, a special grammar or language that can be
used to construct arguments.
When I have used mathematics in my work, I have used it primarily to
explore the nature of evidential argument.
It
is fortunate (or perhaps it was just inevitable) that evidential
argument has been the focus of my sporadic efforts to use mathematics
in my scholarship. The role of argument in inference has been my
focus because I strongly believe that human beings do not directly
perceive the world that they believe surrounds them; I have long
believed that human beings use their minds, brains, and senses to
construct the world, to form images of the world that they believe or
assume surrounds them. Give this, it should be apparent why I think
that argument – including
mathematical evidential argument – is subjective.
And given this, you can understand why I reject the notion that an
argument about evidence couched in mathematical language is an
algorithm, or a fixed formal recipe for the solution of an evidential
problem. Logically valid arguments can and do produce false
conclusions. (For example, a formally valid argument may rest on
false premises.) Finally,
it should now also be
apparent why I do not believe that an evidential argument couched in
mathematical language is necessarily a “model” of actual
evidential inference. The reason is the same as before: an argument
is an argument – whether mathematical language is used to make the
argument or not. For me, mathematics is a guide to the nature of
certain kinds of argument.
Although
I believe evidential argument and evidential inference are
necessarily subjective, I do not believe that inference from evidence
is or should be nothing more than an act of free creation or pure
invention. I am too much of an admirer of science and common sense to
believe any such thing. In most legal settings the aim of factual
inference is to produce factual conclusions that have a good chance
of being true, that have a good chance of approximating actual events
and states of affairs in the world. For this reason, if for no other,
it is fortunate that legal systems worthy of the name demand that
important factual conclusions must rest on at least some evidence: a
requirement of evidentiary support imposes at least some
veritistic (truth-seeking) constraints on fact-finding.
But although I concluded
that that evidence and argument are two essential ingredients of
reliable factual inference, I also reached the conclusion that these
two ingredients cannot by themselves explain how human inference in
legal settings actually works or how it should work. Although the
requirement of evidentiary support insures that some of the premises
of an argument about facts have a basis in evidence, a bare
requirement of evidentiary support allows the formation of distinct
valid inferential arguments that lead to a variety of factual
conclusions, including disparate factual conclusions. This
consideration, along with my experience as a litigator in law
practice and my experience more generally as a human being in the
world, led me to the conclusion that any adequate account of the
actual or proper working of factual inference must take intuition
into account.
But
to assign intuition a central role in fact-finding in the legal
process is almost a show-stopper. That's because “intuition”
seems to refer to beliefs, principles, propositions, and other such
matters, or matters that are not arrived at through conscious
deliberation but are simply given or implicit, that just happen to be
there in our minds, in our brains, or somewhere else in ourselves.
If this is what intuition is, and if fact-finding in the legal
process is importantly driven by intuitions, it hardly seems possible
to regulate fact-finding in a rational fashion. The notion of
rational intuitive inference appears to be an oxymoron! This is the
puzzle I have wrestled with most of my working life.
Although
I may strike you as an unduly obsessive fellow, allow me to say that
I believe and I hope I have made some progress in solving the puzzle
about the relationship between reason and intuition in inference. One
of my insights (which is not necessarily an original insight) is that
the answer to the question of the role of reason and intuition in
inference cannot be given in either/or form: the correct answer
cannot be that inference is always driven either by reason or
intuition but not by both. Reason and intuition both play a central
role in inference.
In
addition, the boundary between intuition and reason is not fixed, it
is not immutable. When I engage in introspection, I often conclude
that many of my intuitions are at least in part a product of my
earlier conscious ruminations (sometimes, to be sure, very
fragmentary and disordered ruminations, but conscious ruminations
nonetheless). If my experience is not atypical and if it is not a
product of delusion, perhaps it is possible to get decision makers
who are involved in the legal process to reflect on and sometimes
revise the intuitions with which they begin; evidence and argument
can be directed at such intuitions.
As
I struggled to work out the role of intuition in fact-finding in the
legal process, it became apparent that such insights, even if valid,
do not guarantee that fact-finding in the legal process will be
accurate. For even if some intuitions are penetrable by reason, human
beings seem to have some or many intuitions that are largely
impenetrable to introspection and deliberation; many of the
intuitions that play a role in fact finding probably lie entirely
beneath reach of conscious thought. So I was forced to confront the
following question: even if we recognize that both intuition and
reason play a role in factual inference and even if we acknowledge
that we can consciously evaluate some of our intuitions, are we
forced, in the end, to conclude that no matter how much we human
beings reflect and deliberate, our factual inferences are generally
not trustworthy because at least some of the premises of our
inferential processes are largely or entirely beyond the reach of
conscious thought – and, for that
reason, are therefore necessarily
untrustworthy?
As
I struggled with this question intermittently, for literally decades
– I consulted literature in fields such as neuroscience, artificial
intelligence, psychology, and cognitive science. I was trying to find
out whether there is much reason or logic involved in subconscious
inferential processes. And much of the literature I examined does
assert or assume that some sort of logic or logics control, regulate,
or structure subconscious inferential processes. To be sure, some of
the literature that I examined emphasizes the fallibility of
subconscious (and conscious) human judgment, inference, and
deliberation. Moreover, none of that literature asserts that human
judgment is infallible. But at least some of the literature asserts
that at least some subconscious human judgments about at least some
aspects of the world are not only produced by natural processes that
are governed by some sort or logics but are also, in the end,
miraculously enough!, fairly reliable.
But
after reaching these conclusions, I was left with a nagging question:
how does the recognition that (a) subconscious inference exists (and
is omnipresent in human inference) and (b) some sort of logic or
logics are involved, bear on the puzzle I posed earlier, that is,
does the unavoidable role of intuition in human inference necessarily
frustrate any effort to make the process of factual inference in the
legal process both rational and reliable? Eventually I arrived at two
conclusions that are pertinent this puzzle – but, as you will see,
they are not entirely reassuring conclusions.
First,
although there is ample reason to
believe that a logic or logics of some kind play a critical role in
subconscious inference, the nature of that logic or logics is not yet
well understood. If that is true, the notion that we might use some
sort of logic-based technology to improve subconscious human
inference in general is only a fantasy at this point in human
history.
Second,
even if we grant the general supposition that subconscious human
inference is "fairly reliable," we cannot extract from this
fuzzy general supposition A. exactly how reliable subconscious human
inference is, and B. the circumstances that render subconscious
human inference either more or less reliable. Given these two
desultory conclusions, does it follow that my extended exploration of
the literature in fields such as artificial intelligence and
cognitive science was pointless?
I
am inclined to think that the literature I examined offers rational
grounds for the hope that two important propositions about human
inference are true:
First,
as I have already said, that
many of our subconscious or
tacit inferences are "fairly reliable." Unlike some
students in the fields of "heuristics and biases" and
behavioral economics, I am impressed by how often human beings get
their inferences right rather than by how often they get their
inferences wrong. A belief in the reliability of much subconscious
inference counsels against too strong a general distrust of the
substrate of subconscious human inference.
Second,
as I noted earlier, even if one supposes (as I do) the existence and
omnipresence of subconscious inference in human inference, it does
not follow that all
subconscious human inference is entirely inaccessible to conscious
thought. Although the structure of some subconscious human
inferential processes is likely to remain entirely impenetrable to
conscious human thought, it is possible as I said earlier, and even
likely, that there are degrees of subconsciousness, and that careful
and persistent deliberation can bring to consciousness some thoughts
and feelings that initially lurk largely beneath conscious awareness,
that swim between consciousness and unconsciousness. If so, as I
noted earlier, it is possible that actors in the legal process can,
with effort, make themselves more conscious of, more attentive to,
more aware of some of the intuitions that seem to play a role in
their thinking about evidence – and it is possible (though not
inevitable) that by doing this such actors will improve the quality
of their inferences.
Of
course, even if I am right about all of this it remains true that a
vast number of subconscious inferential processes will remain largely
beyond the reach of conscious human deliberation and introspection,
and such subconscious inferential processes will remain, by
definition, impervious to conscious critical examination. But perhaps
this is a limitation that we must just accept; perhaps all that we
can ask of human actors is that they deliberate as carefully as they
can about their intuitions and, taking whatever advice they can from
other people and outside sources, decide as carefully as they can.
For the foreseeable future, fact-finding in the legal process
necessarily involves human actors. It
is too much to ask human beings to do more than the best that they
can, but perhaps these insights can help us better understand what
constitutes the best that human beings can do.
