Sunday, 5 April 2009

The Problem Of Induction

It's been put to me a few times by theists when arguing for science, the question of the problem of induction. Not being a philosophy student and being somewhat unfamiliar with where philosophical literature is on the matter, while I had no idea how to respond the argument felt like nothing more than philosophical sophistry. Upon investigation into the concept my suspicions were confirmed. It's a valid criticism though as a problem for science it's far overstated. By focusing on what science isn't, it's deceptive about what science is.

Deductive and inductive logic
It might be wise to explain the difference between deductive and inductive reasoning. Take for instance the deductive proof for abiogenesis:
Life in it's current state can only come from pre-existing life, though such a statement requires an infinite regress.
Since the earth is not eternal, there must have been a point that bore life from non-life.
(Therefore,) abiogenesis occurred.

Deductive reasoning seems easy enough, given a certain set of premises a conclusion can be drawn. In the case of abiogenesis, we understand that the universe and the planet itself is of a finite age. By a variety of dating tequniques and sources, that age is worked out to be ~4.55 billion years. All observation of old rocks and modelling show that the early earth would not be able to cater for even the most primitive of life, so the first 500 million years or so it is deduced that there was no life. By 3.5 billion years ago, the fossil record suggests the presence of primitive bacteria. So it's logical to deduce that somewhere between 4 and 3.5 billion years ago life began on this planet. How it began though is still unknown.

Take one of the premises - life in it's current state can only come from pre-existing life. This is inductive reasoning. Rather it should say, by all observation life can only come from pre-existing life. It's inductive reasoning to infer from observation to apply it on a universal level. The classic example is the black swan. By observing only white swans, the statement "all swans are white" could be inducted. But finding a swan with black feathers falsifies that statement - as it happened when British explorers came to Australia. Taking what is observed and inducing it will always be the case is no guarantee of success.

Practical induction
Say you are holding a glass, after you take a sip you want to free your hands. So what do you do? Any reasonable person will use the law of gravity to make the inductive assumption that a glass needs to be put on a stable flat surface, yet even though every time gravity has worked so far you cannot tell if in the next instance the glass will simply float if you let go in mid-air. Now think of what to do next time the car needs filling up. Now you could stick to petroleum under the inductive purpose that the laws of physics haven't modified your engine, though by doing so you are missing out on the chance to see whether in this one particular instance whether the car will run on pure H2O.

These examples sound absurd but they highlight the way in which induction is used in everyday life. When choosing to exit a tall building, it could be that by jumping out a 10th story window that you'll float gently to the ground, But the safe bet is that while you can't be certain of your demise through doing such a thing, it's it's all probability best to take an elevator and exit through the front door. By turning on a television or getting water from a tap, the inductive reasoning holds true the laws of nature. It's the mastery of the environment, the ability to control these forces, that highlight the triumph of the scientific endeavour.

Turning on the news should show more inductive reasoning in action. Each day during the weather forecast, predictions for what time sunrise will be and the times for the tides are displayed for all to see. These aren't guesses but are worked out through the knowledge of the relationship between the sun, earth and moon. The predictions hold true day after day, this knowledge yet another demonstration that the practical output of induction based on deductive reasoning has merit. The examples of the practical applications of the scientific method are endless, and that that in itself demonstrates is that the process is not hindered by the problem of induction.

At the heart of science is falsification. As Popper noted, it only takes one instance of falsification to show that a logical statement is wrong. For the statement "all radiocarbon dating is accurate", it has been found several different ways where the technique is invalid - such as dating coal or crustaceans. All carbon dating is falsified, but there are still instances where "radiocarbon dating is valid" still holds true. And that's what scientific theories are largely about - finding the best-fit explanation in terms of it's explanatory power of current data and it's predictive power of future data.

It leaves science itself in a state that can never be certain, but that hardly matters. As is evident by modern society the process has been repeatedly shown to work. Ken Miller said during the Dover trial that all scientific knowledge should be regarded as tentative. Look at the way Darwin changed the world in 1859 and Einstein in 1905. Those men in the last 150 years have completely changed the human understanding of the universe, yet like all ideas both of theirs are subject to the same revision as any scientific concept. General relativity still needs to be resolved with quantum gravity, and evolution has changed through observation and experiment. The system is not perfect, but that's the power of science. Those focusing on trying to have certainty will be almost certainly wrong.
"Science must begin with myths, and with the criticism of myths; neither with the collection of observations, nor with the invention of experiments, but with the critical discussion of myths, and of magical techniques and practices. The scientific tradition is distinguished from the pre-scientific tradition in having two layers. Like the latter, it passes on its theories; but it also passes on a critical attitude towards them. The theories are passed on, not as dogmas, but rather with the challenge to discuss them and improve upon them." - Karl Popper

No comments: