| 'Arguably' is a passive word, a word beloved of inexperienced, dilettante writers, often young, often writing about things far beyond their direct experience. It is both lazy and a betrayal of the writer's insecurity, the eight-letter equivalent of essays which begin "I know this isn't any good, but you might like it". Passivity invites attack, and 'arguably' is an extremely passive word. It holds less meaning than 'probably' or 'possibly', whilst creating the impression that the opinion stated by the writer is or has also held by a mysterious other, an anonymous third party which might be God, Death, Orgasm or the Void. When one uses the word 'arguably' one is invoking spirits, dust. There is no iron in 'arguably'. There is only 'gua' and 'arg' and 'bly'.
Its continued popularity is a product of two factors. Firstly, it lends an air of respectability to otherwise facile opinions. To state that "PRODUCT A is the best product by PRODUCER N" is perfectly adequate provided one has made a convincing case that this is so. But many writers are unable to make convincing cases, and such a bald statement may appear hasty or shallow in the infant hands of the baby Jesus. Furthermore, if one has already stated that PRODUCTS B, C, and F are the 'best' products of the mysterious PRODUCER N, a further iteration of this opinion holds no water. The simple inclusion of 'arguably' (or its more florid cousin, "many argue that") serves to add weight to untenable arguments, and to absolve the writer of responsibility for his or her writing. It is the literary equivalent of abandoning a child by the roadside, whether because one is disappointed with the child or because one is unwilling or unable to fight for it.
Writers also use the word 'arguably' because they do not want to seem arrogant. Youngsters live in the extremes and cannot appreciate shades of meaning. To the young mind all viewpoints are either weak or strong, full or empty. The young mind cannot understand that one can argue an opinion without creating undue ripples in the pond, or that the pond itself might teem with dragons. Such an opinion would no doubt be ignored, for one cannot change a leopard's spots with argument alone, but that is a separate issue. I deal with matters of the pen rather than the penis, matters of Eve rather than of the sleeve.
When one is confronted by the word 'arguably' one should question, as one should always question; who is arguing this point? The writer, or his imaginary big brother? Why is this position 'arguable', and not definite? What are the terms of the argument? Just as the exhaust of a space rocket requires the presence of cosmic ether against which to push, so an argument requires a counter-argument. It takes more work and more time to identify and explain the parties, terms and opinions which make up an argument, but there is plenty of time, and writing is hard.
Some defend 'arguably' as a valid weapon in a world of shadows, a world without absolutes, a world where opinions fight for space on the shifting sands, beneath which lurk worms to devour the unwary. Yet the sand is of our own making, just as dust is a conglomeration of the human particle. Beneath the sand is rock, and beneath the rock is steel. I strike you down. | 
