Monday, June 07, 2004


History Through Its Own Eyes

I want to include a lot of history in these essays. It's more a personal interest than a necessity, though. Many things, from human anatomy to the structure of U.S. presidential elections, make sense only if you know where they come from. Science, though, is not always like this. Each of the physical sciences, physics, chemistry, and astronomy, has its own set of theoretical principles. Chemistry and astronomy use ideas from physics, applied to different areas of nature. They are all to some extent the same science, though, so you have subjects like physical chemistry and astrophysics. The basic principles are often called by the name of the originator, but often the principle doesn't depend on the authority of the originator. On the other hand, the social sciences, psychology and sociology, often tend to identify with one or another individual.

Biology is somewhere in between. Darwin tends to dominate evolutionary thinking, but biologists don't cite Darwin as an authority in the same way that anthropologists cite individuals. Much of the thinking in developmental biology (our main concern here) is based on chemistry, so there is less room for individual opinion. Living things are complicated, though, and there are lots of things that biologists would like to know but can't figure out all at once. So there is room for individual opinions. Issues that involve populations of organisms are often murky; the debates over punctuated equilibrium and sexual selection are examples.

In studying the history of science we have to be careful to avoid what some historians call "Whig history". The Whigs were a political party in England (and in the U.S. until 1856). They were supporters of the English constitution, and tended to view history in terms of their own beliefs. In the history of science this view interprets history in reference to an up-to-date science textbook. Greeks who believed in atoms are heroes, those who didn't are stuck-in-the-mud. For example, Janet Browne, in her biography of Charles Darwin, talks about Charles Lyell, whose geological theory influenced Darwin's thnking:
Lyell turned history to his advantage by giving a long and cleverly argued account of the course of geological endeavour from antiquity to the nineteenth century in which everyone who held the same general idea as he did was praised and the the rest dismissed as "unscientific" in blatantly one-sided style. Like the Whig historians whom he greatly admired, he recreated the history of his subject from the position of the author, not just as one in which the past creaked panifully towards the present, but also as a story in which certain inviolate truhts of nature and liberal principles of thought (as seen by Lyell) were progressively revealed to scholars through the ages.
The problem is that nobody in the past was up to our date in all respects. All scientific thinking happens within a world view, a basic belief in what the world is and how it works. The Greeks who rejected atoms (from the Greek atomos, indivisible) believed that matter could be divided indefinitely. The others couldn't accept infinite division; they believed that there are atoms and the void. Anti-atomists couldn't accept the void, a place where there was nothing.

It is tempting to say that the atomists were on to something, and the anti-atomists were misguided. But atoms as we now know them (or think we know!) came from experiments in which chemists found that elements always combined in definite proportions, which implies that there are particles involved. (Of course we also "know" that atoms are actually divisible into elementary particles, which are themselves composed of quarks.) (The "think" and quotes will be explained next time.)

Usually the world view helps science progress, because it tells you what you can look for. Sometimes, though, it holds progress back. We'll see this especially when we get to Galileo. Occasionally somebody will challenge the world view. If the challenge is successful (which is pretty rare) we call the challenger a "visionary", if not he is a "crank".

Most historians feel that western scientific thought started with the Greek philosophers. Usually we think of Plato and Aristotle, although Plato got many of his ideas from Pythagoras and others.

The world view of the Greeks was enough different from our own that it takes a considerable effort to understand Greek thinking. Benjamin Jowett gives some of this in his introduction to his translation of Plato's dialogue Timaeus.Jowett says that one of the reasons for the obscurity of Greek thinking is that it arose "in the infancy of physical science, out of the confusion of theological, mathematical, and physiological notions, out of the desire to conceive the whole of nature without any adequate knowledge of the parts, and from a greater perception of similarities which lie on the surface than of differences which are hidden from view". Much of what will come in these essays will deal with changes in these aspects.

As one example, Greeks saw that animals move by themselves, and rocks don't. Animals are alive, so the Greeks thought that anything that moves by itself, like a planet, is alive. They also thought in terms of "nature", by which they meant "the nature of a thing". Aristotle believed that there are four elemental substances: Earth, air, fire, and water. A stone is earth, and falls because it is its "nature" to go to the earth. The nature of a rock is to be at rest. Smoke is air, so it is in its "nature" to become part of the air.

Aristotle believed that the planets are carried by crystaline spheres. They have to be spheres, because the only motion that can persist is uniform motion in a perfect circle.

Plato, following Pythagoras, held that "everything is number". This can be taken, in our time, to mean that everything follows mathematical principles. This attitude is an important part of our own world view. The physicist Eugene Wigner, for instance spoke of "The Unreasonable Effectiveness of Mathematics in the Natural Sciences". But this can be a handicap in understanding biology. Evelyn Fox Keller, in her book Making Sense of Life, talks about the ways in which the thinking of biologists is different from that of physicists. (More of that in a later essay.)

Physics and biology look at the world from different directions. Mainly, physicists want to explain the world in as few equations as possible, while biologists want to understand living things. Physicists have a powerful tool, but they pay for it in the limitation to simple systems. The motion of two bodies, for instance the earth and the moon, or the sun and a planet, is explainable. Three bodies are explainable only in special circumstances, such as the Lagrange points. Systems of many bodies can sometimes be explained statistically, as in gases.

Biology is different. All biology is local. Biologists have given up looking for top-down rules for how organisms develop; the organism will surprise you. Eventually these essays will take up these topics in detail.

Biology is organized chemistry, so it follows the laws of chemistry. Chemistry follows the laws of quantum mechanics. So biology follows quantum mechanics. The different thing about biology, though, is that there are a great many influences on a growing organism. A planet will always follow its orbit, because it has only its momentum and gravity. An organism has lots more things, which we'll get into later.

In leaning over backwards to understand the past, though, we have to be careful that we don't fall on our behinds. Some philosophers seem to argue that all knowledge is conventional, and that there really isn't any progress. But we feel confident in saying that the earth moves, and that there is no such thing as phlogiston. Again, more later.

Browne, Janet. Charles Darwin: Voyaging, A Biography. Princeton University Press, 1995.


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