Those men who are full of noxious humours, that is to say, full of inordinate inclination towards bodily comfort and towards foreign and creaturely consolations, can fall into four kinds of fever.
The first kind is called the quotidian fever. It is a multiplicity of the heart; for these men wish to know all things, and to speak of all things, and to criticise and to judge all things, and meanwhile they often fail to observe themselves. They are weighed down by many strange cares; they must often hear what they do not like; and the least thing troubles them. Their thoughts are restless; first this, then that, first here, then there; they are like to the winds. This is a daily fever; for they are troubled, and busied, and in multiplicity, from morning until evening, and sometimes in the night also, whether they sleep or wake. Though this may exist in a state of grace and without mortal sin, yet it hinders inwardness and inward practices and takes away the taste of God and of all virtues. And this is an eternal loss.
The second kind of fever comes on alternate days. It is called fickleness. If it lasts long it is often dangerous. This fever is of two kinds: sometimes it comes from intemperate heat, and sometimes from cold. The one which comes from intemperate heat befalls certain good men; for when they are, or have been, touched by God, and then are forsaken of Him, they sometimes fall into fickleness. To-day they choose one way of life, and to-morrow another; at one time they wish to be silent, and another time they wish continually to speak. First they wish to enter into this order, then into that. First they wish to give all their goods to God, then they wish to keep them. At one time they wish to wander abroad, at another to be enclosed in a cell. At one time they long to go often to the Sacrament, and shortly afterwards they value this but little. At one time they wish to pray much in a loud voice, and another time but shortly after, they would keep silence. And this is both a vain curiosity and a fickleness, which hinder and impede a man from comprehending inward truth, and destroy in him both the source and the practice of all inwardness. Now mark whence this unstable condition comes in some good men. When a man sets his thoughts and his inward active endeavour on the virtues and on outward behaviour more than on God and on union with God: though he remains in the grace of God (for in the virtues he aims at God), yet none the less his life is unstable, for he does not feel himself to rest in God above all virtues. And therefore he possesses something that he does not know; for, Him Whom he seeks in the virtues and in the multiplicity of acts, he possesses within himself, above intention, above virtues, and above all ways and means. And therefore, if this man would overcome his fickleness, he must learn to rest above all virtues in God and in the most high Unity of God.
The other fever of fickleness, which comes from cold, all those men have who love God indeed, but at the same time seek and inordinately love some other thing. This fever comes from cold, for the heat of charity is poor indeed where not God alone, but foreign things besides and with God, urge and excite us towards the works of virtue. Such men are fickle of heart; for in all the things which they do, nature is secretly seeking its own, often without their knowledge, for they know not themselves. Such men choose and abandon, first one way of life, then another. To-day they choose one priest, to whom they would go for confession and for counsel their whole life long; and to-morrow they will choose another. On all things they will ask advice, but hardly ever do they act upon it. All things for which they are blamed and rebuked they like to excuse and to justify. Of fine words they have plenty, but little is in them. They like well to have a reputation for virtue, but without great effort. They wish their virtues to be known, and these are therefore empty, and have no savour either of God nor of themselves. Others they teach, but will themselves hardly be taught or reproved. A natural self-love and a hidden pride make them thus fickle. Such people walk on the verge of hell: one false step, and into it they fall.
In some men this fever of fickleness may produce the quartan fever; that is, an estrangement from God and from themselves and from truth and from all virtues. And then they fall into such confusion that they are at their wit's end and know not what to do. This illness is more dangerous than either of the others.
Through this estrangement a man sometimes falls into a fever which is called the double quartan, which means indifference. Then the fourth day is doubled, and he can hardly recover, for he becomes indifferent and heedless of all that is needful to eternal life. So he may fall into sin, like one who never knew anything of God. If this may befall those men who govern themselves ill in this state of abandonment, then it behoves those to beware who never knew ought of God, nor of the inward life, nor of that sweet savour which good men find in their exercises.