A couple of weeks ago, on an evening of drinking and philosophizing, a friend asked me this question and I did not have any answer then.

Chris Anderson’s video about giving TED talks kept popping into my mind; I remembered it mostly for the pretty visuals it had representing what an idea is. But I could not extract out an exact definition from it. Just this morning, as I was reading Siddhartha Mukherjee’s book about genes, the answer popped into my mind.

An idea is a “mental gene”. It is any thought pattern that can be transmitted and copied from one mind to another.

Ideas can be simple or complex, verbal, visual, auditory, or relating to touch or some combination of these. Whatever they are, the defining property of an idea is that it can be transmitted from one mind to another. During the process of copying, the original idea often gets corrupted, i.e. it mutates and evolves.

In much the same way that a gene is a unit of physical heredity - that in humans it is manifested in the DNA is an independent fact - an idea is a unit of mental “heredity”. It can be passed from one mind to another through various means: words (spoken or written), art, music, etc.

Depending on the environment and circumstances, an idea gets expressed into action and is then visible to the world. The idea of atheism must have always existed in small scales throughout human history, but it was only when science was sufficiently advanced that it expressed itself into politics as the “separation of church and state”. The same idea is also expressed differently within different individuals. The idea of mathematics can produce joy in one and revulsion in another.

When there is a mismatch between an idea and reality, we get a disease (e.g. religion), very analogous to genetic diseases. Unfortunately, unlike human genes which reside in a single molecule, we do not understand how these mental genes are stored, and their propagation is much more complex and multi-faceted which makes idea diseases much harder to cure.

The biggest difference between human genes and ideas is that human genes are determined at the conception, whereas ideas can be assimilated into a (sufficiently open and malleable) mind far into adulthood. Hence, ideas evolve at a much faster rate than genes.

This is of course very similar to Richard Dawkins’ meme. It might even be the same thing. I am not entirely sure as I haven’t read much about it.