Multipathism is the ism which states that all entities in the universe follow multiple paths through time. That is, a single event can lead to may outcomes, and each of those outcomes actually occurs (though an observer may only recall experiencing one of them). Similarly, every situation can be the result of many causes, and each of those causes actually occurs.
In effect, it says that the fifth dimension is formed of parallel possibilities.
Evidence for multipathism
The best intuitive evidence for multipathism lies in quantum mechanics. QM says that the position (and momentum) of a particle can be represented by a wave of possibilities. For example, an electron in a certain orbit around a nucleus can be thought of as a "cloud" of possibilities. We do not know exactly where it is, just where it is most likely to be. Only when we observe and take measurement of a particle does it collapse into a definite location. Strangely, when we accurately determine the position of a particle, we can no longer determine where it is going (its momentum).
The many-worlds interpretation of QM states that each and every one of a particle's position/momentum possibilities exists in its own "world". When we observe the electron and find it is position A, there are also separate worlds in which we observe the electron to be in positions B, C, D, and so on. This is consistent with (and perhaps identical to) multipathism.
The possibilities that can arise from a complex event are endless, almost*. When a ball rolls off of a table, it will most likely fall down to the floor, but there is a smaller possibility that it will mysteriously float up to the ceiling. This is a tenet of quantum mechanics - you can never predict what a particle (or a group of particles) will do. Perhaps 99.9999% of the time the ball will drop straight down, but there is still a 0.0001% chance something unexpected will happen (anything that happens only 0.0001% of the time must be unexpected!).
* It is important to note that the possibilities are never truly endless. Infinity does not exist. In the case of the ball, the farthest it can move one second after it rolls off the edge of the table is 299,792,458 meters away. This is dictated by the speed of light and Einstein's rule that nothing can go faster than it.
Large Numbers of Possibilities
In some special places, like the center of the sun, or on earth, there is much complexity and energy, leading to a very high number of possibilities for the system. In particular, humans and human society (which are both kulti) can lead to a high number of possibilities. See complexity singularity.
Humans and multipathism
If each human follows multiple paths, it is implied that every possible scenario for your life will actually occur. Do we experience all of these scenarios? Seemingly not - we experience only one present, and we remember only one past. However, experience is entirely defined by memora (=essentially memory). It's possible that we do not have access to the memories of other paths. This implies exocognism.
Can we chose the path we experience? Of course we can, we do that every day with our actions.
It is important to remember, as we talk about pasts and futures, that time is personal. There is no universal past or future. At any one time, my neighbour and I may recall vastly different pasts. Well, of course we have different pasts - what I mean is that the very set of facts contained in our pasts may differ. In his past he may recall the Canucks winning the Stanley Cup and Al Gore becoming president, though I know those never happened.
Likewise, my neighbour may go off and experience a future that has a completely different set of facts.
Reconciling contradictory paths between two people
If my neighbour and I have different sets facts in our pasts, how can we possibly interact? Logic must always be preserved.
As long as the facts that we share do not contradict, then logic is preserved. My neighbour and I could still have some contradictory facts in our pasts, but as long as we don't discuss them or allow them to become shared then everything is okay. If my neighbour's past includes the fact that the capital of Italy is Venice, and my past includes the fact that it's Rome, then so be it, there is no contradiction in either of our (personal) universes as long as we are never forced to reconcile the two facts.
So what will happen if my neighbour and I start talking about Italy and its capital? Well, any of my neighbour's pasts that include Venice as the capital will instantly be pruned from my (personal) universe. Those pasts do not lead to this present. It may be that we act the observer, and in much the same way a particle's wave function collapses into a single state when observed, another person's pasts will collapse into only those that do not contradict our own.
The role of memory in multiple pasts
It's easy to imagine the present diverging into multiple futures. But can multiple pasts converge into the present? You might wonder how the present you are experiencing could possibly arise from any other past than the one you remember. It might seem that if the past were even slightly altered it would lead to a wholy different experience in the present - in effect, for every present there is one and only one past that could have led to it. This idea appears in science fiction stories, in which time travellers are always extra-cautious to avoid altering the past, so that when they return to the present it is still the same.
Imagine a simple scenario. A person, let's call him Joe, enters a one-room house, and then leaves. Now imagine that there are two pasts: in one past the inside walls of the house were blue, in the other they were orange. As long as Joe doesn't remember what color the walls were, and as long as he cannot see the walls anymore, then both of those pasts could lead to the same present.
So, it would seem that the potential pasts that lead to your present would be only limited to those that don't contradict your present memories and observations (that is, your experience).