The Search after Therefore, being presently delivered from the prejudices that led us to believe that our efforts are very powerful, and that those of the subtle matter that surrounds and compresses hard bodies are very weak, and being persuaded besides of the violent agitation of this matter in virtue of the things I said about gunpowder, it will not be difficult to see that it is absolutely necessary that this matter must be the cause of the hardness of bodies or of the resistance we feel when we try to break them apart.