ADDITION , the basic arithmetic operation, is not quite so straightforward and unambiguous as one might suppose. When we ‘add’ one thing to another, or to a collection, the originally separate items remain separate after combination : they do not fuse or merge.

Addition is a strictly numerical operation which tells us nothing about the sizes of the objects that are brought together, nor their colour, mass and so forth. The only assumption made is that the items with which arithmetic  deals are discrete and remain so. Even when dealing with liquids which do combine together imperceptibly to form a whole, we often tend to still think in terms of discrete items : when we talk of ‘adding’ a bucketful of water to a pond, the implication is that the water in the pond is made up of ‘so many bucketfuls’, i.e. could be broken down into units. If we want to take merging into account we end up with the formula 1 + 1  = 1  which, though it is a perfectly correct representation of what goes on when, say, we combine two droplets of rainwater, looks extremely peculiar. It would be quite possible, though probably not worthwhile, to develop ‘Rainwater Arithmetic’ where no matter how many items you add together the net result is 1. Many liquids have an upper limit to merging : if you carry on adding droplets of oil to an initial droplet lying on water, the sheet of oil eventually splits in two. In such a case 1 + 100,000,000 = 2 or something of that order of magnitude. Our arithmetic, then, concerns entities with an upper limit of 1 , i.e. substances which never merge at all or, if they do , immediately break apart.

There are at least three different senses to addition which we might call  ‘adding’, ‘adding on’ and ‘adding up’. In the first case we join together two groups or collections of comparable size. In the second case we tack on a smaller collection to a larger, and in the third case we do not so much join together as rearrange. In abstract mathematics there is no difference in the operations involved but in concrete terms there is all the difference in the world.

The most ancient of the three types of addition is undoubtedly ‘adding on’. If we go back to the time when objects or events were recorded by notches on a bone or knots in a cord (which I shall call the tally system) there is nothing to ‘add up’ because there is no numerical base : what is on the stick or bone is the ‘total’ and that’s all there is to it.  A new item, the birth of a child or a caribou kill, will be recorded at the end of the list which will, if there are very few items most likely be arranged in a row, or in several rows more or less underneath each other as on the Ishango bone, perhaps the earliest example of written numerals. In Wild West days, Billy the Kid “had so many notches on his gun” — one notch, one dead person. The amount grows by accretion just like an organism : the longer the list the more items, children born, midsummers, caribou kills and so on.

But when you add ciphered numbers the final amount does not grow noticeably  : 2 + 3 = 5 where 5 is no larger or longer than 2 or 3. This is not in the least a trivial observation since it is the root cause of the current very widespread misunderstanding of what numbers essentially are, namely the symbolic representation of real or imaginary collections of certain objects, collections which increase or diminish in size.

And when you add up a column of figures all you are doing is getting the separate amounts into a tidier form. What was separate (distinct) before addition remains separate after addition : the difference is that the whole lot is now grouped in a systematic fashion according to the powers of the base, usually ten. But what is there at the end was there at the beginning.

However, when you ‘add’ fresh recruits to a regiment, new employees to a firm’s workforce or money to someone’s bank account you are not just rearranging what is already there but bringing in someone or something new from outside. It is at first sight somewhat surprising that this makes no difference arithmetically speaking, the reason being that by the time the new objects are actually joined to the existing group they are no longer completely ‘new’ since they are already in existence, even if, as in the case of an ‘addition’ to a family they have only just been born.

Despite the difference between adding up and adding on, the operation of addition remains, like division, an ‘inert’ one : strictly speaking nothing is created or destroyed. A primary schoolteacher teaching addition to a child has to have the extra building blocks required concealed to one side : if there is nothing there to add, addition cannot take place. This is quite distinct from a truly ‘creative’ operation where something new is produced from within as when a mother gives birth or when unicellular organisms like bacteria reproduce by splitting in two (mitosis). I did as a matter of fact start to  construct an arithmetical system where the basic operations are splitting and merging instead of adding and subtracting.   SH  14/9/13