In the literature on synchronicities, that phenomenon is usually defined as a coincidence of two or more events which invokes a “sense of meaningfulness”, and where the events in question — crucially for the point I want to focus on — are not causally linked.
In one respect, that last clause is a sensible requirement. For if there were a causal link between those events, that would suffice as explanation, and there would be no reason for further inquiry. (We must keep in mind, however, that it really is ‘everyday’ causality we are talking about here, not a scientific or formal philosophical notion.) It seems reasonable, therefore, to focus only on those situations where such a causal connection cannot be found.
However, it is one thing to put the exclusion clause into the definition, and quite another to blot out from our investigation those situations which will be excluded by it. True, they do not, by definition, fall under the notion of synchronicities, i.e. they are not considered instances of the phenomenon. But it would be rash to remove them from the discussion: for they provide a helpful comparison class when we look at that elusive feature of “a sense of meaningfulness”.
1. The impression of meaningfulness can be investigated in various ways. We might look at it phenomenologically, that is, try to understand it from the particular subjective quality of how it feels. The suggestion there of course is that there is a specific, perhaps unique quality to be found here; and Jung, when he makes that suggestion (see e.g. GW VIII, §§827, 841), occasionally alludes to Rudolf Otto’s well-known specification of a “numinous” feeling. Such a suggestion (though not of course the phenomenological direction of investigation as such) thereby associates synchronicities with religious experience, expressions of mystic qualities, and perhaps even sensations induced by psychedelic drugs, which have been linked with such types of religious experience, phenomenologically.
But once we look at synchronicities together with the comparison class I mentioned above (those situations where there actually is a causal connection between coincidental events), another route of investigation opens up.
2. Let’s take a pair of examples to illustrate. For a coincidence that falls under the notion of a synchronicity, we can re-use one that I have already used previously. In that scenario, I reconnected, on a sudden impulse, with a friend from my university time, of whom I had not heard for a while. That same day, another friend from that same period of my life sent me an email to reconnect, too. It seemed a remarkable coincidence that it happened on the same day; the sense of meaningfulness was further intensified by the fact that I had already been thinking about refreshing old ties in the run-up to the episode. There was, however, no causal connection between the two events (they happened independently of each other: those two friends had not been in mutual contact). Thus it was a case of a synchronicity.
Now compare the following scenario: Suppose I have recently been divorced, or at any rate become “single again”. One of my friends invites me to a dinner with her husband on the weekend; and when I arrive there, just “by accident” there is another guest, an acquaintance of my friends, who is also single. Just a coincidence? Perhaps. But then two weeks later, I’m on a trip with another friend of mine, and once more, “somehow” it just happens that I become introduced to another person from their social circle who might be a “good match”… You get the picture. Clearly, some matchmaking is going on here, and therefore, this is certainly not a case of mere coincidence. Of course, the matchmaking may well be unconscious, or, even if it is somewhat deliberate, my friends may still act independent of each other: there is no need to suspect conspiracies. (But I admit it’s not a coincidence that the scenario is reminiscent of a 1990’s movie.)
3. In the second scenario, just as in the first one, there may well be a sense of meaningfulness in the subject (i.e., “me”). That impression would vanish soon, however, once the causal connection clearly emerges. Once I see through the matchmaking efforts of my friends, I will have difficulties taking the naive romantic view that things are going on which are “meant to be” (whatever it is, precisely, that is expressed in such phrases).
So the moment we understand that there is a causal explanation for a coincidence (i.e. that it is not a synchronicity, as we defined the term), the sense of meaningfulness disappears. It seems strongly indicated, therefore, that the sense of meaningfulness is a feature of the subject’s interpretation of what is going on, an aspect of the subject’s framing of the situation.
Note, however, that this is not necessarily a question of whether there is a causal connection. If there is one, and the subject merely does not know it (or doesn’t want to hear about it), there can still be a sense of meaning. Whether a connection objectively holds is less important than whether the subject sees the world (frames the situation) in terms of that objective fact.
4. Thus we may think of synchronicities and their comparison class (coincidences with an everyday causal explanation) on a spectrum ranging from situations where the subject frames the circumstances in terms of a causal interpretation (my friends are actively arranging for me to meet new people as potential romantic mates) to situations where the subject cannot (or would not) frame them in such a way, but rather by invoking a “sense of meaningfulness”.
Both ends of the spectrum have in common that “someone or something” arranges the events in the particular manner the subject experiences. On the end of the spectrum where there are causal explanations, that “someone” is of course the agent who caused the situation (the matchmaking friends); on the synchronicities end of the spectrum, there is no such agent, but the subject may imagine some placeholder “agent”, commonly using such expressions as “the gods want to test my patience” or “the universe is conspiring to assist me”. Typically, the subject does not have a considered opinion about the existence of “the gods” or the activities of “the universe” — those are merely helpful “as if”-expressions used for the framing. Imagining them does not entail a supposition of their objective existence; they can be merely a projective construct with a helpful function in the framing process.
Of course, on both ends (and indeed, at any point the entire spectrum over), the subject’s framing presupposes that there is “something like” a causal agent who arranges things. In other words: the subject has a blind spot when it comes to the possibility of mere coincidence, stark randomness. It seems that, especially in everyday situations, there is a strong bias to assume a causal agent (instead of mere coincidence) — and thus, if none can be perceived, the need for “stand-ins” such as “the universe”. This property of the framing process (and its relative strength in individual subjects) is of course a fitting subject for empirical investigation, and I’m not going to follow it up for the moment.
But independent of that, we might notice that there is still this remarkable connection, in situations with synchronicities, between framing with a “stand-in” and the “sense of meaningfulness”. Once the subject can reframe the situation as one with an everyday agent (matchmaking friends), it vanishes. The sense of meaning is clearly tied to the “stand-ins”.