Chapter 3 looks at what Feynman calls "The great Conservation Principles". He looks at conservation of quantities like charge, energy, momentum and angular momentum. Feynman observes that, as far as we can tell today, what he terms the "great" conservation laws are absolutely accurate. Some others are only approximate, but are still useful. In concluding this chapter, Feynman writes (emphasis is mine):
"Discovering the laws of physics is like trying to put together the pieces of a jigsaw puzzle. We have all these different pieces, and today they are proliferating rapidly. Many of them are lying about and cannot be fitted with the other ones. How do we know that they belong together? How do we know that they are really all part of one as yet incomplete picture? We are not sure, and it worries us to some extent, but we get encouragement from the common characteristics of several pieces. They all show blue sky, or they are all made out of the same kind of wood. All the various physical laws obey the same conservation principles."
Towards the end of a chapter on the distinction between past and future, Feynman writes as follows:
".. an understanding of physical laws does not necessarily give you an understanding of things of significance in the world in any direct way. The details of real experience are often very far from the fundamental laws. We have a way of discussing the world, when we talk of it at various hierarchies or levels... For example, we have at one end fundamental laws of physics. Then we invent terms for concepts which are approximate, which have, we believe, their ultimate explanation in terms of the fundamental laws. For instance, 'heat'."
Feynman outlines an ascent up a continuing "hierarchy of complexity" to the features of living beings (again, emphasis is mine).
"And then we go on, and we come to words and concepts like 'man', and 'history', or 'political expediency', and so forth, a series of concepts that we use to understand things at an ever higher level. And going on, we come to things like evil, and beauty, and hope ...
"Which end is nearer to God; if I may use a religious metaphor. Beauty and hope, or the fundamental laws? I think that the right way, of course, is to say that what we have to look at is the whole structural interconnection of the thing; and that all the sciences, and not just the sciences, but all the efforts of intellectual kinds, are an endeavour to see the connections of the hierarchies, to connect beauty to history, to connect history to man's psychology, man's psychology to the working of the brain, the brain to the neural impulse, the neural impulse to the chemistry, and so forth, up and down, both ways...
"And I do not think either end is nearer to God... And to stand with evil and beauty and hope, or to stand with the fundamental laws, hoping that way to get a deep understanding of the whole world, with that aspect alone, is a mistake. It is not sensible for the ones who specialise at one end, and the ones who specialise at the other end, to have such a disregard for each other. (They don't actually, but people say they do). The great mass of workers in between, connecting one step to another, are improving all the time our understanding of the world ... and in that way we are gradually understanding this tremendous world of interconnecting hierarchies."
Leaving aside for the moment the references to God, and what these references tell us about Richard Feynman's views on religion, there is here a clear affirmation that the physical sciences alone are not able to tell us everything about the world. At the very least, the human sciences must also be engaged. The reference to such ideas as evil, beauty and hope suggests that philosophy must be involved in our search to understand the world - as well as physics.
In this context, the last two paragraphs of the whole book are interesting (emphases are again mine):
"In this age people are experiencing a delight, the tremendous delight that you get when you guess how nature will work in a new situation never seen before. From experiments and information in a certain range you can guess what is going to happen in a region where no one has ever explored before...
"What is it about nature that lets this happen, that it is possible to guess from one part what the rest is going to do? This is an unscientific question: I do not know how to answer it, and therefore I am going to give an unscientific answer. I think it is because nature has a simplicity and therefore a great beauty."
I want to suggest that, in saying that the question is "unscientific" and in giving an "unscientific answer", Feynman is recognising that the question takes him from one level in the hierarchy of connections to another. The question is a philosophical one, not one about the physical laws themselves. It therefore deserves a philosophical answer, that is, an "unscientific answer", and not an answer determined from the physical laws themselves. The descriptor "unscientific" does not imply any illegitimacy in either the question or the answer. Or at least this is what I would like to think Feynman meant to say, though I must admit to not being absolutely sure that it is what he meant.
The reference to "simplicity" and "great beauty" can be clearly related to the suggestions of a unity in the physical world indicated above.