In addition to what has been said already - and prompted by Leo's last post, with which I agree - I'd like to share a short reflection I've had on this card. I have only just received the deck - it was waiting for me as I got home. On the way home, I heard a fascinating programme on the radio, about neuroscience and ethics. There was a lot in it, but this item particularly struck me: in the past 10-15 years, and thanks to neuro-imaging (MRIs and the like), it has become possible to show what many had intuitively grasped before: that emotions play a crucial role in creating consciousness. In particular, emotions (not feelings, I mean emotional reactions such as shivering or increased heartbeat, etc.), precede ethics and social behaviour, and are a necessary condition for ethical behaviour and socialisation. Emotions are situated mainly in the frontal lobe, and when it is impaired, patients lose the capacity to make moral and ethical choices. They can still reason - but they no longer have a "conscience". The frontal lobe is one of the oldest parts of the brain - it was formed long before humans were humans, when our forebears were still animals - and it has evolved very little. But the rest of the brain - in particular the larger part capable of reasoning and invention, evolved later and is still evolving. Reasoning can only become ethical choice after the emotions have played their role and triggered a feeling - pity, anger, indignation, etc. - at which point reasoning builds a moral structure on the foundations of the emotions.
When I took out the deck and looked at the card, it occurred to me that here was an image of the original emotion that precedes moral choice and socialisation, but is a necessary condition for them. The Wild Hersdman is all emotion - his heartbeat will increase or he will start shivering and that guides him immediately in a direct reaction. He is at a stage of proto-ethics, if you like, before reasoning has taken hold of what is happening and built a moral and social structure, but he already acts morally, without reasoning - instinctively. That's how I understand "pre-civilisation".
The reason why such a creature would appear evil to a religion (Christianity) that puts such a high value on morals, is because he has not built a formal moral structure, and so his emotions very evidently rule him. More "evolved" human beings have fooled themselves that their ethics are based on reason, not on emotion...we know better now! The Wild Herdsman is our moral foundation and without him, we have no ethics and cannot make any moral choice. He is our shadow in as much as we fear the power of our emotions. Those who resist emotions are perhaps those who are truly bound and obsessed, in the sense the Devil card has in other decks. But those who accept the role of emotion and work with their emotions, and with the feelings these evoke, are more likely to make moral choices that are loving and useful - in fact, are truly ethical.
The Horned One is removed from the society of men and is often rejected by them, though he also fascinates - as though to show how we often reject and repress our emotions.