The central idea of consilience.

How does Wilson define consilience? The best description I found in the book is here:

The central idea of the consilience world view is that all tangible phenomena, from the birth of stars to the workings of social institutions, are based on material processes that are ultimately reducible, however long and tortuous the sequences, to the laws of physics. In support of this idea is the conclusion of biologists that humanity is kin to all other life forms by common descent.

(Edward O. Wilson: p. 266)

Now, we should be careful to distinguish this position from a simple-minded mechanicism. Those who oppose science as a limited form of knowledge —yes, it's not only the Americans who oppose it in the name of religion; here in Europe there are plenty of people who oppose the scientific worldview in the name of a badly understood humanism that stresses the arts and considers anything that's related to science and technology as something "too cold and inhuman"— like to criticize this position as "reductionism". However, this is not what Wilson proposes. First of all, we should be careful when equating the laws of physics with good old mechanicism. That might have been true of the classical mechanics, the Newtonian physics of yesteryear, but today's physics are far more complex than that. To think that resorting to the laws of physics to explain the phenomena we observe is reductionist (in the sense of stupidly simplistic) is quite naive or, even worse, ignorant. Today's physics is nothing but overly complex and more than capable of accepting non-deterministic behaviors in its theories. Second, and most importantly, Wilson's objective is to find a field of knowledge that could make it possible to synthesize all human knowledge (i.e., the theory of everything that we have been after lately), and to be fair physics seems to be the discipline that is getting closest to that. The social sciences are, without any doubt, way too far from objective knowledge in any form or shape. There are only two positions that we can take regarding this issue: either we continue their original project, convinced that it is possible to study the human being in an objective manner, or we just give up in despair and choose to stress that human nature is different, which seems to be the Postmodern approach. It's clear to us which is Wilson's preferred option: he chooses to reaffirm the validity of the Enlightenment and its project of universal knowledge.

There is one more criticism of the scientific mindset that Wilson also deals with. Those who oppose the scientific methodology as the best way to achieve knowledge, emphasize the fragmentary nature of our knowledge these days. There is an excess of information everywhere, they remind us. Not only that but, for each possible explanation or theory that we hear about a particular fact, there always are several other alternative approaches. Worse yet, we have no way to figure out which one is correct. Postmodernism loves this position, emphasizing fragmentation and plurality and dismissing science as dogmatic, bent on imposing a single true explanation that, in reality, nobody can prove beyond any doubt. As I said, Wilson also addresses this issue:

Thanks to science and technology, access to factual knowledge of all kinds is rising exponentially while dropping in unit cost. It is destined to become global and democratic. Soon it will be available everywhere on television and computer screens. What then? The answer is clear: synthesis. We are drowning in information, while starving for wisdom. The world henceforth will be run by synthesizers, people able to put together the right information at the right time, think critically about it, and make important choices wisely.

(Edward O. Wilson: p. 269)

In other words, he doesn't deny the existence of a plurality of explanations. He doesn't believe in the imposition of the Truth either. I think we all understand that these days. Yes, we have somehow internalized the postmodern criticism —which is at least partially valid— that, even if we accept the existence of an objective reality out there, our own knowledge of it may always be partial, incomplete, imperfect. And yet, we cannot just give up and fall back into an affirmation of subjectivity, like the postmodern thinkers do. Sure, a dogmatic belief in an objective Truth could potentially lead to a totalitarian ideology, but a simple look back at our own History will also teach us that nihilism has the very same effect: the lack of an objective way to measure things agreed upon by all social agents leads to the world of the jungle, where the stronger imposes his will over everybody else. Wilson knows all that. He knows the dangers of both dogmatism and nihilism. What he proposes is a firm belief in the scientific method as the best possible way to achieve knowledge, even if he fully understands this knowledge will always be limited and partial. That is, nevertheless, no reason to give up, especially when science has already proven to be the only methodology that got us closer to real knowledge of how things work. I have to agree with him.