From this illustration Augustine leaps at once to his final inference that only the Trinity--Father, Son, and Holy Spirit--is to be enjoyed.[60] It follows as a corollary that the important knowledge for man is that which will bring him to God surely and for eternity. Such is knowledge of Holy Writ and its teachings. Other knowledge is valuable as it aids us to this. Proceeding from this point of view, Augustine speaks more specifically. To understand Scripture one needs to know the words and also the things referred to. Knowledge of the latter is useful, because it sheds light on their figurative significance. For example, to know the serpent’s habit of presenting its whole body to the assailant, in order to protect its head, helps to understand our Lord’s command to be wise as serpents, and for the sake of our Head, which is Christ, present our whole bodies to the persecutors. Again, the statement that the serpent rids itself of its skin by squeezing through a narrow hole, accords with the Scriptural injunction to imitate the serpent’s wisdom, and put off the old man that we may put on the new, and in a narrow place--Enter ye in at the strait gate, says the Lord.[61] The writer gives a rule for deciding whether in any instance a literal or figurative interpretation of Scripture should be employed, a rule representing a phase of the idealizing way of treating facts which began with Plato or before him, and through many channels entered the practice of Christian doctors. “Whatever in the divine word cannot properly be referred to _morum honestas_ or _fidei veritas_ is to be taken figuratively. The first pertains to love of God and one’s neighbour; the second to knowing God and one’s neighbour.”[62] Augustine then refers to matters of human invention, like the letters of the alphabet, which are useful to know. History also is well, as it helps us to understand Scripture; and a knowledge of physical objects will help us to understand the Scriptural references. Likewise a moderate knowledge of rhetoric and dialectic enables one the better to understand and expound Scripture. Some men have made useful vocabularies of the Scriptural Hebrew and Syriac words and compends of history, which throw light on Scriptural questions. So, to save Christians from needless labour, I think it would be well if some one would make a general description of unknown places, animals, plants and minerals, and other things mentioned in Scripture; and the same might be done as to the _numbers_ which Scripture uses. These suggestions were curiously prophetic. Christians were soon to produce just such compends, as will be seen when noticing the labours of Isidore of Seville.[63] Augustine speaks sometimes in scorn and sometimes in sorrow of those who remain ignorant of God, and learn philosophies, or deem that they achieve something great by curiously examining into that universal mass of matter which we call the world.[64]