Just what is the role of Mercury on your birth chart? Why does it seem to be ‘neutral’ – neither masculine nor feminine? Most of all, how should we even begin to interpret it? It’s true that Mercury is often overlooked in both chart interpretation and progressions-transits to the natal chart. But, being neither boisterous nor ego-oriented like the Fire planets, nor strongly emotional and feeling toned (like the Water planets Venus and the moon) looking at its sign or house position alone may not tell you much about an individual’s behaviour. This is because its function is all about the hidden-from-view processes of consciousness.

Mercury is traditionally the ‘communicator’, just as the house he ‘rules’ (the 3rd) is associated with all forms of communication and its devices (which can include newspapers, televisions, telephones, the Internet etc.) Better still, Mercury is the secret transmitter of information, or that which translates raw data into something intelligible. In this latter role, Mercury is the Logos, for the early Stoic philosophers the ‘active reason pervading and animating the universe’ (according to Wikipedia) or, for Christianity, that which makes God knowable and intelligible, as with John’s gospel where Jesus Christ is the incarnate Logos. (Thus to understand Jesus gives us an idea of God’s true nature.) So it is the principle of turning ‘information’ into human knowledge, or consciousness.

Mercury’s fundamental role is to make intelligible that which is inchoate or merely raw data. The whole phenomenon of speech is an example of this – at some stage in history we managed to improve our communication skills by using verbal cues to refer to objects outside of the self. (Human language was thus on the way to becoming the sophisticated entity that it is today.) But this process of data conversion works thus: suppose you’re tuned to your favourite radio station – what’s really happening here? Well, before the broadcast from the station reaches you it has been converted or encoded into electrical signals or waves (at a particular frequency) that are sent through the atmosphere. These would be useless without your radio – a device which converts these signals back into their original state so you can hear what’s being broadcast.

Mercury is that process of conversion, or transduction. The human nervous system, it could be said, works in much the same way – as sense impressions become conscious experience via ‘data’ travelling through the nerves to the brain which is then apparently ‘translated’ into colours, tastes, sound, warmth-cold, the smell of freshly baked bread. That is, consciousness. But without this transduction process we would sense nothing! We could say that Mercury is that which makes consciousness possible. (Mercury, naturally, ‘rules’ the human nervous system in Medical Astrology.)

But there is something  we haven’t mentioned yet – Mercury’s ‘dual’ nature (in that, as we’ve observed, he seems to be both Masculine and Feminine.)  In ancient metaphysical views of Creation, Duality is born when the One Consciousness in creation wants to know itself. The undivided Self becomes aware of Not-Self in order to apprehend its own inner nature. This is why the world contains a multiplicity of opposites: male-female/day-night/good-evil/father-mother. This Duality (an archetype in itself) makes it possible for us humans to differentiate, and thus discriminate, judge and make rational decisions, or simply to see clearly another point of view. Rather like the Adam and Eve myth, only when Eve had eaten from the Tree of Knowledge of Good and Evil, did the pair become truly aware of a world beyond the Garden which had hitherto kept them in a state of blissful, womb-like ignorance. Their world (the undifferentiated One) was, sure enough, split asunder as they were banished from Eden (Duality), but in the process they became conscious, knowing beings.

Mercury is a little like the crafty serpent in Eden, and in Greek myth Mercury – the so called messenger of the gods – likewise gets up to all kinds of mischief. Some of this was seemingly cruel, as when he persuades a tortoise to leave its shell, after which he eats the poor creature. He’d told it that it would make wonderful music when dead – which was true, because Mercury (or rather Hermes, to give him his Greek name) proceeded to invent the lyre from the entrails of a slaughtered cow and the tortoise’s shell. Here is Mercury-Hermes in his role as the archetypal Trickster (whose counterparts can be found in many Native American myths, too). In the human world he represents everything that is wily, clever, versatile, restless or changeable (hence our common adjective ‘mercurial’).

As we’ve noted, Mercury is androgynous, often personified in Greek myth as an eternal youth, swift and fleet of foot. But this asexuality is a metaphor – he is neither ‘positive’ nor ‘negative’, good nor bad. Rather, he is something in-between – the grey betwixt black and white, partaking of both. Take the seven original planets and class them as polar opposites – then you get Sun (dynamic Self) vs. Moon (inner emotions); Venus (relationship) vs. Mars (selfish ego) and Jupiter (expansion) vs. Saturn (limitation). Mercury is the odd one out, for it really can’t be said to have an opposite – it is a symbol of integration and greater consciousness.

Mercury on the Birth Chart

Mercury is really about how our minds process information, how we ‘get’ something. If it’s in an earth sign, things are understood in ‘black and white’ terms, usually slowly and methodically, with an eye to their usefulness. (Though there may be little appreciation of nuance and subtlety, as a result.) If Mercury is in a Fire sign, you grasp things quicker, more intuitively, probably jumping to conclusions before rapidly moving on. If it’s in a Water sign, the world is understood in a more feeling-toned, holistic way, where things are not simply either-or, good or evil, spirit or matter, but relative to one another. (You normally see the ‘grey’, as opposed to the black and white mentality of Earth.) And your perceptions are – like Fire – intuitive and instinctive. Mercury in Air, however, enjoys ideas and facts for their own sake – and usually can explain just how they arrived at a certain conclusion. The pure realm of reason and logic is how they prefer to operate though, unlike Earth, they enjoy abstractions too (the sphere of symbolism, metaphor and analogues beloved of philosophers).

When Mercury does pertain to some obvious aspect of your character, this is because it’s in powerful aspect to a planet. If the sun or Mars, we get the loquacious type with plenty to say for themselves. Such people usually have an abundance of nervous energy, though may also lack mental focus and concentration. If Mercury aspects Venus we find the refined charmer with good social, even artistic, skills; when Mercury aspects Saturn, there is the taciturn, laconic individual, who nevertheless compensates with thoroughness, a focus on small details, and a more practical turn of mind.

So Mercury (unlike the sun, or Mars) tends not to be an obvious personality ‘factor’ in its own right. You need to see what planet it’s aspecting, or if it connects with any of the angles. This will give you an idea of how a person is inputting information, and their capacity for awareness, for Consciousness. But you can be certain that, without Mercury, there simply would be no Consciousness at all!