The sensuous impulsion excludes from its subject all autonomy and freedom; the formal impulsion excludes all dependence and passivity. But the exclusion of freedom is physical necessity; the exclusion of passivity is moral necessity. Thus the two impulsions subdue the mind: the former to the laws of nature, the latter to the laws of reason. It results from this that the instinct of play, which unites the double action of the two other instincts, will content the mind at once morally and physically. Hence, as it suppresses all that is contingent, it will also suppress all coercion, and will set man free physically and morally. When we welcome with effusion some one who deserves our contempt, we feel painfully that _nature is constrained_. When we have a hostile feeling against a person who commands our esteem, we feel painfully the _constraint of reason_. But if this person inspires us with interest, and also wins our esteem, the constraint of feeling vanishes together with the constraint of reason, and we begin to love him, that is to say, to play, to take recreation, at once with our inclination and our esteem. Moreover, as the sensuous impulsion controls us physically, and the formal impulsion morally, the former makes our formal constitution contingent, and the latter makes our material constitution contingent, that is to say, there is contingence in the agreement of our happiness with our perfection, and reciprocally. The instinct of play, in which both act in concert, will render both our formal and our material constitution contingent; accordingly, our perfection and our happiness in like manner. And on the other hand, exactly because it makes _both of them_ contingent, and because the contingent disappears with necessity, it will suppress this contingence in both, and will thus give form to matter and reality to form. In proportion that it will lessen the dynamic influence of feeling and passion, it will place them in harmony with rational ideas, and by taking from the laws of reason their moral constraint, it will reconcile them with the interest of the senses. LETTER XV. I approach continually nearer to the end to which I lead you, by a path offering few attractions. Be pleased to follow me a few steps further, and a large horizon will open up to you, and a delightful prospect will reward you for the labor of the way.