You can choose to believe in determinism if you like, but in the end, we are obliged to feel that we have free will.
There are many related but slightly different concepts.
Aetiology (US = etiology) relates to causation: A causes B causes C and so on until the eventual outcome. This is a "snooker balls" view of how things and events interact in chronological sequence. It is often useful in everyday life.
Teleology is in some ways the opposite: the idea that things and events are drawn towards an ultimate goal. Teleology as an idea easily becomes contaminated with the idea of "purpose" or "intention" although purpose and intention can only occur where there is a conscious mind to have that purpose or intention.
Someone who favours the aetiological view might point to the effect of hard work, poor diet, disease, and the gradual breaking down of the replication of DNA and conclude that these things "cause" someone to grow old and die.
Someone who favours the teleological view might point to the need for each new generation to have space to live, resources such as food and water, one earlier generation to help to look after the children, and no substantially older generations to be a burden. In this view, the decline and death of the older individual is caused by the need for the next generation to thrive.
Causation is the concept that events are caused by previous events. If you had perfect knowledge of all of the facts then you would be able to start from one point in time and work forwards or backwards to make accurate predictions about what you would find. In a sense, the "direction of time" is irrelevant to causation, although it remains relevant to us because of the way that we experience the events.
Randomness is when events of a similar nature do not occur in a predictable pattern. However, there are two ways that this can arise:
- There is no pattern at all.
- We can never have enough information to be able make the prediction.
Consider the tossing of a coin. The outcome will depend to a greater lesser degree on the position and energy state of every molecule in the coin, every molecule of air in the room, and every molecule in the body of the person tossing the coin — and many other factors.
It would be impossible to collate all of this information. Even if, for the sake of argument, it took 1 nanosecond to gather it all, some of the variables would have changed between collecting details of the first molecule and details of the last. Therefore, our calculations would inevitably be slightly out. When we take a snapshot on a digital camera, the information for each pixel is saved at a slightly different time. The differences are infinitesimal, but they are there.
Chaos theory shows that sometimes, a tiny change in initial conditions can have a substantial effect on the outcome. Rather than looking at this as a mathematical theory, consider the effect of a single pebble on a busy road road being thrown up by the wheel of a truck. The tiniest change in one of the variables could make the difference between the pebble hitting the bonnet (hood) of a car, or the windscreen (windshield), or hitting a motorcyclist and knocking him off his bike and killing him. Millions of pebbles are thrown up by wheels every day. Most do no damage, some chip paintwork, a few smash windscreens, and occasionally someone is killed. Sometimes the biker is killed and his bike slides harmlessly down the road and sometimes it causes a major pile up. All of this variation is because the pebble was a milligramme heavier, or slightly smoother, or the truck's tyres were 0.1 bar higher or lower in pressure, or, or, or...
- Destiny is generally positive. Your life leads ultimately to success. "He was destined for great things."
- Fate is more ambivalent. "They were fated to meet and fall in love," or "A terrible fate awaited him."
- Doom is always bad. "Prepare to meet thy doom." "He was doomed to die."
In fact, Destiny, fate, doom, wyrd, kismet, star crossed, etc. are all the same thing: labels that we attach to sequences of events and their outcomes because humans like to ascribe a narrative and a meaning to things.
So back to the original question. I met my wife through a dating website. It was just over a year after I had separated from a former partner and I was ready to start dating. It was about the same length of time since she had separated from a former partner. I chose the website solely because a friend had used it successfully: he now lives with a girl he met via the site.
The website offered me several thousand "matches" and I narrowed the search terms down slightly. One short sentence in her profile caught my attention. I contacted her. We both happened to be free a day or two later. We met and fell in love.
If we look at the chain of causation, I can identify many fortunate coincidences. If I believed in destiny, or fate, I might say we were destined or fated to meet.
- My friend who recommended the website had used other websites, It was only luck that he met his fiancée through that particular one.
- I met that friend on my first night at fencing club.
- I went to that fencing club only because they had a beginners' course starting only a few days after I searched for fencing clubs in my area.
- I searched on that particular day because I had seen a picture of a unicyclist in fencing gear in the unicycle forum. I have never seen a picture of a unicyclist in fencing gear before or since.
- I had started unicycling only because I happened to see a unicyclist at an event that I seldom attended.
- And so on.
Of course all of the timings and details of other life events mattered as well. The chances on meeting my wife were a proverbial million to one. The point is, if I hadn't met her, I would not have known, and would probably have met someone else and been approximately as happy. I might then have felt that I had been "fated" or "destined" to meet her.
Was it predestined? Only if I am selective in which facts I include in my narrative.
Did I have free will? Did she? It certainly felt like it.
Was that free will decision in reality dictated by the position and energy level of every molecule in my system and hers? Possibly, but as this information could never conceivably have been accurately collated and studied, it is a meaningless question.
In life, we make a small number of decisions. Most of what we do is habit or whim, or responding unthinkingly to social stimuli. However, that does not mean that there is no element of free will. Sometimes we make big decisions deliberately and after careful thought. Are they caused by our previous experiences and our desires? Yes, in a sense, but if they had no cause at all, they would be meaningless.
Buridan's ass was a hypothetical donkey, placed equidistant between two bales of hay that were equally attractive. If the forces of attraction (donkey attracted to food) were exactly and perfectly equal, a donkey with no free will would starve. However, none of us believes that the donkey would starve. He would choose which one to eat first.
If Buridan had instead postulated a metal pin placed exactly and perfectly equidistant between two perfectly identical magnets, the pin would stay there indefinitely. A pin has no free will.