187. These, then, are the services of fortitude; and full they are of virtuous and seemly duties. But in all that we do we must look to see, not only if it is virtuous, but whether it is possible, so that we may not enter upon anything that we cannot carry out. Cic. de Off. I. 21, § 73. Wherefore the Lord, to use His own word, wills us to flee in the time of persecution from one city to another; S. Matt. x. 23. so that no one, whilst longing for the crown of martyrdom, may put himself in the way of dangers which possibly the weak flesh or a mind indulged could not bear and endure.