The first time I read this verse I was struck by its simplicity. It’s written clearly: not prevaricating or making excuses for itself, but putting a fairly extreme claim in as few words as possible. The meat here is mainly philosophical – aside from the wonderful clarity of expression, there’s little to recommend this verse from an aesthetic standpoint.
Let’s examine the meaning. The heart, the verse starts, setting a metaphorical tone. What is the ‘heart’ here? In my opinion it represents emotion, gut feeling and animal impulse: the Platonian urges that are conquered by Reason. The heart is deceitful, we hear, which is a little surprising. The idea that the heart represents a reliable compass, a true guide, is very popular: phrases like ‘follow your heart’ attest to that. But not only does this verse tell us that the heart is deceitful, it tells us that it’s deceitful above all else.
We know what this means, though. Hearts are tricky things, not above cajoling or using trickery when simple persuasion fails. In fact, the extremes of emotion – rage, hatred, fear, passion – are responsible for awful things. The chilly logic of a utilitarian as he sacrifices lives for the greater good is shocking in its ruthlessness and inhumanity, but for most of us the real ethical challenge is in conquering our knee-jerk fear or anger. Jeremiah is talking about that animal part of us, what Freud (pronounced ‘fraud) would have called the id. He judges it to be not just wicked, but desperately wicked – a metaphor that captures the stress that accompanies crimes of passion. Not for nothing are criminals often called ‘desperate men’.
He finishes with a question – who can know it? – that seems counter-intuitive. Isn’t the heart the deepest part of ourselves, the part that we know most well? The heart – that kernel of emotions and passions – is us, insofar as any part of ourselves makes up our identity. But Jeremiah’s right: what makes our feelings so dangerous is that we too often don’t understand and can’t predict them.
In a world full of conflict and outside threats, this verse turns the focus inward. It mocks the kind of person who sits in judgement of other people’s hearts, not understanding his own. If we can’t set our own house in order, how can we criticize other people? Perhaps we can’t – but even if we can, we ought to start with ourselves.