The main reason for this talk is that atheism and atheists have been beset over the years with false or "straw man" definitions, descriptions and requirements, emanating mainly from people opposed to atheism and seeking to discredit or malign atheism and atheists. Some of what I regard as malignant definitions have proved very persistent, particularly in societies where levels of theistic beliefs are high.

I used as the nucleus of what I am going to say an article of mine, "My Atheism", which was published in the Australian Atheist in late 2010.

Those of us here who were brought up in a mainly western European culture should remember that, for more than a millennium, Trinitarian Christianity, essentially the Catholic Church, held immense legal and social power over the entire population. Minorities such as Jews were subject to restriction and persecution, and heterodox opinions such as Catharism, Unitarianism and atheism could carry the death penalty. Church attendance was made compulsory in England on several occasions, the last one being probably the Act of Uniformity of 1662. Even after unorthodox views and beliefs ceased to be illegal, blasphemy laws remained in force, and it was often economically and socially unwise to admit that you did not assent to the official or principal religion of the country, be it Catholic or later Protestant.

In a letter to New Scientist, published on 7 April 2012, David Bennett claimed that "the main tools" used by the world’s most successful religions to keep and enhance their dominance were force and violence. He asserted that "The dominance of Christianity is the result of centuries of colonialism and imperialism. The spread of Islam was the result of conquest rather than conversion." I think he is on the right track, but some of us may have doubts about whether this would apply to, say, Buddhism.

"Force and violence", wrote Bennett, "are not only a way of gaining new adherents, but also stop critical examination of the preached religion. Bullying and intimidation have proved, and still prove, capable of silencing opponents. The ongoing history of inquisitions, oppressive fatwas and executions bears testimony to this."

I suspect that, although Christian triumphalism may not have made cowards of us all, it made many people timid and wary of admitting that they did not share the beliefs of the majority, particularly if they were also the beliefs of the ruling and employing classes. One of the tasks of atheist, freethought, humanist, rationalist and secularist organisations is, I submit, to help people overcome the remains of this cultural and philosophical cringe that still makes some people embarrassed about declaring that they are not believers.

Nevertheless, although atheists and atheism have been maligned and misrepresented in the past, what atheists have had to put up with has been nowhere near as vicious as the canards, lies and misinformation Jews have had to contend with for centuries from anti-Semites. And if most Jews have had the intestinal fortitude still to call themselves Jews, either in the cultural or religious sense, or both, then it is high time atheists showed and advocated adequate levels of intellectual and moral courage. I am not here this evening to salve the consciences of timid non-believers.

Now I do not claim that there is a one-and-only correct definition of atheism, or that my definition is the last word on the subject. I have been an atheist since about the age or ten or eleven, or since roughly 1954. I regard myself as an atheist because my answer to the question "Do you believe in God?" is simply no.

The words atheist and atheism come, through French athéisme, from the Greek ’????? (atheos), meaning without or denying god, godless, or (rarely) abandoned by the gods. It consists of ????, god, the same as Latin deus, and of the prefix ’?-, equivalent to the Latin in- and non- and the English prefix un- and suffix -less, signifying without, free of or the absence of.

Atheism, then, is lack of theism, of belief in a god or gods, although philosophers sometimes distinguish between theism, belief in a personal god who still affects the physical world and may be supernaturally revealed; and deism, belief in a divine principle or creator god who does not normally interfere in the ordinary world and the affairs of people. Just to complicate matters, deism is sometimes used in the sense of believing in a supreme being as a result of reasoning instead of from revelation. In these senses I am both an atheist and a non-deist.

Although I have given you the etymology of atheism, may I caution you against the notion that etymology defines the only acceptable meaning of a word. It most certainly does not. The etymology of muscle is musculus, a little mouse, from Latin m?s (the same in Greek); but a muscle is not a little mouse, it is a fibrous animal tissue with the capacity to contract. But some muscles look vaguely mouse-shaped. Sesquipedalian is Latin, meaning a foot and a half, but in modern English it means full of long words, polysyllabic or cumbrous or, in the case of someone like me, long-winded and pedantic. Everyone here knows what a dream is, but it comes from the Old English word dr?am which, a thousand years ago, meant joy, ecstasy or music. Atheism has the same etymology from Greek as non-deism does from Latin but, as I have already tried to explain, atheism and non-deism do not have completely identical meanings today.

In Western cultures, at any rate, atheism is generally taken to mean disbelief in the Judaeo-Christian or Abrahamic deity God with a capital G, a title transmuted into a name for Yahweh, Jehovah or El, called Allah by Muslims. A long time ago Christians were regarded as atheists because some denied the existence of the gods and goddesses of Greece and Rome, while others regarded these deities as demons, but almost nobody uses atheist and atheism in this sense any more. Modern atheists do not believe in the god of monotheism (God) and, as a rule, they usually disbelieve in the supernatural altogether.

Mano Singham, writing in the July 2011 New Humanist (London), reckons that a more accurate definition of an atheist would be "One for whom God is unnecessary as an explanatory concept".

He also thinks the notion of denial needs clarification. "It is the word ‘denies’ that creates problems. If by ‘denies’ we mean a willingness to publicly declare disbelief, then it . . . is acceptable. But if interpreted as implying that the atheist is certain that there is no God, then it is too strong. Since one cannot prove the non-existence of a god, or anything else, no thoughtful atheist would sign on to such a statement."

Some people distinguish between "hard" and "soft" forms of atheism; and there is also a grey or unclear dividing line between atheism and misotheism, the latter being the notion that, whether God actually exists or not, God or the orthodox concept of God is evil and harmful. The irreligious poetry of Shelley and Swinburne contains strong misotheistic overtones as, I suspect, do some of the writings of Nietzsche.

Jonathan Lanman, in a New Scientist (26 March 2011) article, "Thou shalt believe — or not", explores in detail the difference between what he calls "non-theism", namely "the lack of belief in the existence of supernatural agents", and "the moral opposition to religious beliefs and values" which he terms "strong atheism". Being a pedantic old man, I do not like non-theism, because it is a mixture of Greek and Latin — but so is television! Lanman adds: "The majority of Danes are non-theistic; few are strong atheists", though he mentions later that many Danes joined the Danish Atheist Society "after the Muhammed cartoon controversy".

Lanman explains that, during the twentieth century, Scandinavian governments set up "extensive welfare policies for ethnically homogenous populations". He writes that, as a result, "Fewer economic and social threats meant less religious action and, in the span of a generation, levels of theism fell". On the other hand, the United States "instituted comparatively weak social welfare policies for a more divided population. Consequently, it saw little decline in theism."

Lanman’s opinion is that, "while I think that a lack of social and economic threat produces non-theism, I believe that higher levels of threat to a particular vision of society help produce strong atheism. Strong atheism is not the absence of an in-group ideology but the defence of one: modern secularism."

Part of Lanman’s evidence is the contrast between the United States and Denmark: "In the US, where many Christian conservatives make no secret of their desire to govern by ‘Biblical’ principles, we find hundreds of atheist organisations and thousands of people expressing the view that religion is immoral and to be combated through argument. In Denmark and Sweden, with little threat of politicians governing by religious principles, we find fewer atheist organisations and, in organisations that do exist, much less activity."

Lanman’s article is worth reading, whether you agree with all of it or not. And I suspect that the rising fortunes of the National Secular Society in Britain and the Atheist Foundation of Australia here during and since the first decade of the twenty-first century may well be linked to privileges granted to religious organisations by socially conservative Christian politicians and also to the rise of Islamist jihadism and fundamentalism.

I think we now need to look at some of the straw-man or Aunt Sally definitions of atheism concocted by people who dislike atheism. I maintain it is important that we do not allow ourselves to be led astray by them. For example, atheists do not have to "believe in" an entity called "no God" in order to qualify as atheists. Atheists do not have to "prove" that "no God" exists or that God does not exist. Indeed, when asked to prove that God, alias Jehovah, Yahweh and so on, exists, the usual theist fudge is to tell us that we have to have "faith" instead — as if wanting proof is disrespectful. Many atheists, myself included, simply do not "believe in", in other words we lack faith in the religious sense — of a strongly-held emotional conviction. This view appears to be shared by the American writer, George H. Smith, in Atheism: The Case Against God (1979): "Atheism in its basic form is not a belief: it is the absence of belief. An atheist is not primarily a person who believes that god does not exist; rather, he does not believe in the existence of a god."

Another false argument is that "you can’t be an atheist" unless first you know all there is to know about a particular religion, religions in general, or even everything in the universe. No, you do not have to be omniscient to be an atheist; omniscience is an alleged characteristic of God and occasionally of some of the self-important people who claim to be God’s agents or spokesmen on earth.

Similarly you do not have to "know" or be absolutely sure that God does not exist. In a logical sense, you can know that something does not exist only if there is a contradiction or definition mistake in the affirmative version, such as a round square or a married bachelor. We can be certain beyond reasonable doubt — for now — that a silver teapot is not orbiting the Sun between the Earth and Mars, but not absolutely certain.

In any case, as our perceptions of ourselves and the outside world are made through our imperfect senses, we cannot be sure of anything in an absolute sense. I am as sure as I can be that I was conceived and born, that I exist now, and that I will die; but — in high theory, at any rate — all of this could be an illusion or delusion. But I operate on what seems to me the reasonable assumption that I exist, that the external world exists, and that I can usually make sufficient sense of the world to survive and make my way around in it.

One of the main reasons I do not believe in or accept the entity called God is that an omniscient, omnipotent and all-good deity seems a manifest absurdity when I can clearly observe a world around me that is full of misfortune, suffering and injustice. Theologians and clerics have written and preached on this subject at great length, and there is even a technical name for it, theodicy, allegedly "the vindication of divine providence in view of the existence of evil". But large quantities of spin and special pleading are never really convincing. And I am singularly unimpressed by the sophistry that suffering and injustice are the result of "free will" given by God to human beings. After all, much of the suffering, such as that of wild animals, is not connected with human beings. And in any case, God, being omniscient, would be well aware of the consequences of giving free will to the human race.

I am also unimpressed by the notion that God wants us to "believe in", love and worship him. Why? An omnipotent deity would be, by definition, invulnerable and self-sufficient, and could not be harmed or threatened by anything that mere mortals do. A jealous, unhappy or angry god is not omnipotent. And a good and omnipotent god would not be in the least distressed because I or anyone else does not "believe in" or love him. I am reminded of the eighteenth-century Scottish philosopher, David Hume, who wrote that "It is an absurdity to believe that the Deity has human passions and one of the lowest of human passions, an appetite for applause."

Despite all the efforts of modern theologians to reinvent or to redefine God in terms such as "Love" and "the ground of our being", the demanding, loving, punitive god of much evangelical, hard-line, authoritarian theism still sounds suspiciously like a Bronze Age Middle Eastern warlord or absolute monarch, particularly when his followers claim he and they have been offended or treated with insufficient respect or subservience. Indeed, we should not lose sight during the semantic sleight-of-hand performances of religious orators and writers that one of the essential functions of many conventional religions is to provide power, prestige and privilege for the people who run religions.

Religious authoritarians often insist that their so-called sacred beliefs be treated with respect. I maintain that people’s rights are entitled to respect, including the right to hold seemingly foolish notions; but religions are not — repeat: are not — entitled to the privilege of special respect, nor is any ideology, opinion, belief or theory. So I staunchly maintain that it is the duty of all with backbones who care about freedom of expression to oppose blasphemy laws.

This does not mean that atheists should browbeat or harass others for their private supernatural beliefs. But it is another matter when religious authoritarians want to censor scepticism or disbelief, or treat atheists and dissenters as second-class citizens. Atheists and freethinkers do have a duty to resist religious triumphalism and privilege.

I suspect that almost everyone here has, at some time or other, heard, read or been told that you cannot be ethical or moral unless you believe in God or at least in the supernatural; and this is despite the appalling behaviour of many believers in a god or gods over the centuries, often in the name of a religion or for the purpose of promoting their faiths. The claim is both hypocritical and false, but has been accepted by many people who have not thought carefully about it. One reason among many for its persistence is that the philosopher John Locke, who wrote A Letter Concerning Toleration in 1689, singled out atheism at the end and wrote: "Lastly, those are not at all to be tolerated who deny the being of a God. Promises, covenants, and oaths, which are the bonds of human society, can have no hold upon an atheist. The taking away of God, though but even in thought, dissolves all; besides also, those that by their atheism undermine and destroy all religion, can have no pretence of religion whereupon to challenge the privilege of a toleration."

It sounds to me as if Locke extends the notion of toleration only to people who have a "pretence of religion". Indeed, Locke goes on to say: "As for other practical opinions, though not absolutely free from all error, if they do not tend to establish domination over others, or civil impunity to the Church in which they are taught, there can be no reason why they should not be tolerated."

I think we can safely assume that "if they do not tend to establish domination over others" refers to the Catholic Church. I understand that Locke’s Letter advocated toleration for Jews and Muslims, so he excluded from toleration only atheists and Catholics, but for different reasons.

A rather different opinion was given recently (5 June 2012) by Nigel Barber, writing in the Huffington Post: "Contrary to the claims of religious leaders, Godless countries are highly moral nations with an unusual level of social trust, economic equality, low crime and a high level of civic engagement. We could do with some of that."

Well before the rise of Christianity, Plato recounted how the Greek philosopher Socrates once had a lengthy argument with a man called Euthyphro about what constituted piety. Euthyphro’s third definition was that what all the gods loved was pious, and what they all hated was impious. Socrates countered this with what philosophers call the Euthyphro dilemma, namely: "Is piety loved by the gods because it is pious, or is something pious because the gods love it?" The point Socrates was making was that the approval of the gods was merely an attribute of piety, but did not actually define piety.

Similar reasoning holds if today we substitute "good" or "moral" for "pious", and God for the gods. Is it good, moral or right because God likes it, or does God like it because it is good? The claim that "God is good" is little more than repetition if good is only "what God wants". Doing something "because God says so" is a choice or decision that may have an ethical component, a form of "carrot and stick" morality, if you like, but it is primarily a decision to obey, and although obedience is sometimes useful, it is not always ethical. Members of criminal gangs can be loyal and obedient to the gang’s psychopathic leader. And since at least 1945 the excuse that "I was only obeying orders" has received scant respect from humane and civilised people, and rightly so.

Human beings are social animals, and there is general agreement that our brains have a natural ability to learn language, though which language will vary with geography and upbringing. I am reasonably confident that we also have an innate capacity for moral decision making, though the precise details of what we come to regard as right and ethical will vary with parenting, culture and experience.

I understand morality as the capacity to make ethical decisions and to act wisely and appropriately on them most of the time. (Yes, because we are fallible, we will occasionally make mistakes.) I also strongly suspect that the human capacity for moral reasoning is nurtured when we are young by seeing others, especially parents, acting ethically. In other words, when it comes to morality, example is probably better than preaching or prescription.

It is probably worth quoting here words from The Kasidah (1853), attributed to Hazi Abdu el-Yezdi, but in fact written by Sir Richard Burton: "Do good for good is good to do; spurn bribe of heaven and threat of hell."

While discussing atheism I probably need to consider agnosticism as well. Again, there seems to be no universal agreement on exactly what agnosticism means.

The word agnostic was coined by Thomas Henry Huxley in 1869 from Greek a-, again meaning non-, not or without, and ????????? (gn?stikos), good at knowing, related to ?????? (gn?sis), knowledge or a judicial inquiry, but later used in European philosophy to signify special knowledge of mystical, supernatural or esoteric wisdom, hence the sect name Gnostics. Today agnostic usually signifies someone who is uncertain or noncommittal about the existence of God, though it can also be used of people who are uncertain of other matters. Further, it can mean someone who claims that nothing is or — so far as we can tell or judge — can be known about the existence of God or of anything beyond, behind or other than material phenomena, in other words denial of gn?sis in the sense of direct supernatural revelation.

Mano Singham, whom I have mentioned earlier, points out that this definition fails to distinguish between not knowing something and there being nothing to know. He quotes the comedian Ricky Gervais as saying: "Since there is nothing to know about God, a comedian knows about as much about God as anyone else."

Mano Singham adds, in his own words: "It is logically impossible to prove the non-existence of anything, however absurd (whether it be a god or unicorns), so the purely logical answer to whether anything exists, when the answer isn’t ‘yes’, is ‘I don’t know’. By this definition we are all agnostic about practically everything."

However, for Huxley agnosticism meant "not a creed but a method", namely, "Positively the principle may be expressed as in matters of intellect, follow your reason as far as it can take you without other considerations. And negatively, in matters of the intellect, do not pretend conclusions are certain that are not demonstrated or demonstrable". Huxley also wrote that "it is wrong for a man to say he is certain of the objective truth of a proposition unless he can produce evidence which logically justifies that certainty." Some commentators, such as the late Dr Gordon Stein, have argued that Huxley’s definition of agnosticism is not clearly distinguishable from the meaning of rationalism, which I understand as the theory that reason is the foundation of certainty in or the ultimate authority in knowledge, or, if you prefer, and I do, the opinion that theories and beliefs should regulated by reason, not authority.

I do not regard myself as an agnostic in the popular modern sense of someone who is not sure if God exists or not. I regard the god of monotheism, God with a capital G, as a monstrous absurdity, and am comfortably confident that such an entity exists only in the imaginations of the faithful. I regard the existence of other gods, goddesses and minor supernatural beings as so remotely unlikely that I can presume they do not exist — and, strangely enough, no one today seems to demand that I must be one hundred per cent convinced that Amon-Ra, Balor of the Evil Eye, Brigit, Bunjil, Danu, Diana, Govannon, Marduk, Mars, Niamh, Nut, Odin, Quetzalcoatl, Sarasvati, Set, Tammuz, Tethra and Thor do not exist.

As for the notion that nothing can be known about gods or the supernatural, well, if supernatural beings did exist, I can see no reason why they should not communicate with mortals from time to time. Why should they be timid or perverse and want to hide themselves?

If magic and supernatural beings really did exist, their existence should be one of the most blazingly clear and obvious things in the world around us. Instead, we are told that we have to "believe in" God, and that, despite the absence of evidence, to doubt his existence is a "sin". It all sounds like a very, very large confidence trick, reminiscent of Hans Christian Andersen’s story of "The Emperor’s New Clothes" (1837), although I do not doubt the sincerity of very many people’s religious faith. On the other hand I notice that most religious beliefs are spread not so much by persuading adults as by the intensive indoctrination of children.

Yes, I might conceivably be wrong about gods and the supernatural, but were I ever to be persuaded that a deity or deities existed, I cannot imagine that this would cause me to subscribe to an authoritarian ideology like orthodox Christianity or Islam. I dislike all totalitarian ideologies, whether theistic, political or otherwise, because they lead to fear, oppression, violence and injustice. And I certainly do not need the bribe of heaven or the threat of hell to make me strive to be a decent human being.

I regard atheism as true, in the sense of being a reliable evaluation of the real world or universe; and for that reason I think atheism is well worth speaking up for, particularly when I consider the vast quantity of effort, money and resources that is still spent on promoting, funding and following theistic religions. However, being an atheist does not mean that I have a key or answer to all the great questions of philosophy, like how did the universe begin — or did it begin? But telling me that God made the universe by magic really tells me very little, and begs a host of other questions. I do not know whether the universe had an ultimate origin, but the mystery for me is that anything exists at all, rather than does not exist, and god-talk does not dispose of this.

Furthermore, being an atheist does not automatically make me wiser or more virtuous than other people. I can be clumsy, fallible, foolish, hasty and thoughtless. I commend to my fellow infidels the semi-facetious but very insightful words of the nineteenth-century English radical M.P., Henry Labouchere: "The mere denial of the existence of God does not entitle a man’s opinion to be taken without scrutiny on matters of greater importance."

Quite so. But I maintain that atheism is still a matter of great importance, and it needs its sincere, thoughtful and careful champions, just as freedom does. According to the Book of Psalms (14:1 & 53:1), "The fool hath said in his heart, There is no God." But wise and good men and women do more than keep their opinions just in their hearts and to themselves: they have the courage to speak out when necessary, to stand up and be counted.