A reader writes:
scientific worldview. The default position for a scientist is to not believe something unless there is a compelling reason to do so – the default is not to be neutral until the weight of evidence tips things one way or the other. For example, if you ask a scientist if s/he believes in unicorns or alien abductions, the answer would be no – not "I don't know". Of course the "no" is not absolute and unchangeable; if compelling evidence is brought forth, then positions can and will change. But if a hypothesis currently fails to be persuasive, then the answer is "no".
This holds for the god question as well. While minds must be open to persuasion, the unpersuaded mind responds "no – I do not believe in god", not "who knows?". Since all scientific knowledge, both positive and negative, is always conditional, relative to evidence, the "who knows" is everpresent in the background. Atheism and agnosticism are synonymous in the scientific worldview.
I'm sure you're going to be deluged by people making similar points, but there's no contradiction between being an agnostic and an atheist (or an agnostic and a theist, for that matter).
Contrary to the popular perception that agnosticism sketches out some middle ground between atheism and theism, which pertains to belief or non-belief in any deities, agnosticism is an orthogonal position that pertains to whether or not it's possible to know whether or not any gods exist (which is why it's antonym is gnosticism).
If you asked either Neil deGrasse Tyson or Richard Dawkins if they believe in any gods, I'm fairly certain that both of them would say no without any hesitation – hence they're atheists. If you asked them whether it's possible to conclusively prove or disprove the non-existence of gods, however, they would both state that such proof is outside the realm of science – thus they are agnostics. I'm also fairly positive that Dawkins, at the least, is perfectly familiar with the distinction and is using the term agnostic with precision.
I think that the confusion that people have over the term comes from the misconception that atheism requires an active and uncompromising assertion that gods do not exist. In philosophical circles, there is a distinction made between positive atheism, which positively asserts that gods don't exist, and negative atheism, which pertains to a simple lack of belief in gods. Unfortunately, the latter – which is, in my experience, where the vast majority of self-identified atheists fall – is too often mistaken for agnosticism by people who aren't familiar with the word's history and its technical meaning.
If you look beneath the whitewashing of skepticism that is the timid brand of "agnosticism" claimed by Neil deGrasse Tyson, you'll find a belief system that is far more dangerous to religion than most exclusively atheistic perspectives are. In particular, the class of agnosticism articulated by T.H. Huxley, who coined the word agnosticism, is a rejection of false certainty, an abnegation of pretense. In fact, this is what Huxley had to say during one particularly amusing exchange with the Catholic apologist W.S. Lilly who was trying to pigeonhole Huxley (amongst others):
The foundation of morality is to have done, once and for all, with lying; to give up pretending to believe that for which there is no evidence, and repeating unintelligible propositions about things beyond the possibilities of knowledge.
In this understanding of agnosticism, those who do not accept the limits of knowledge are liars lacking a foundation for their moral beliefs. The reason why virtually all skeptics, especially scientists, will readily accept a formal label of agnosticism is precisely for this reason. They accept that knowledge is limited. Notably, this is not contradictory with atheism.
If you don't believe in the existence of a God, you're an atheist, but that doesn't mean you have to be a movement Atheist. If you can name yourself a Christian without being tagged as a religious-right evangelical, why can't you admit to being an atheist without people assuming you're a ranting, card-carrying Dawkins disciple?
The embarrassing crowing about Dawkins actually "being an agnostic" pretends that he has either changed his position (he hasn't) or that his beliefs are not actually those of most atheists (they are). Dawkins and Tyson represent very prominent examples of self-described atheists and agnostics everywhere. At their core, they hold the same position, but they disagree about nomenclature. We are hardly the only community with mostly unproductive controversies about definitions (ask any person in the LGBT movement to define "queer"), but this disagreement should not normally be held as evidence of a deep philosophical difference because, most of the time, it's not.
Tyson responded to some pushback on his Big Think appearance here.