Malo nodo malus quaerendus cuneus

A tough and harsh knot, is not to be attempted to be cut by a fine tool; it can only be overcome by the application of a strong wedge. Great difficulties or diseases are not ordinarily subdued, but by powerful remedies, which may not be applied, perhaps, without some degree of danger. The adage also intimates, that in repelling injuries, we may use weapons, or means, similar to those with which we have been attacked. Craft and cunning may therefore be properly had recourse to, in opposing the machinations of the malevolent, and unjust. A horse perceiving that a lion was endeavouring by pretending to be skilful in medicine to entice him into his power, in order to destroy him, asked him to look at a swelling which he affected to have in his foot, and the lion preparing to examine the part, the horse gave him so violent a stroke with his heels, as laid him sprawling on the ground. The adage also means, that a lesser evil is sometimes obliterated by a greater, and one passion or affection of the mind by another.
«Even as one heat another heat expels,
Or as one nail by strength drives out another,
So the remembrance of my former love,
Is by another objet quite forgotten».