Of the two parables setting forth the progressive character of the kingdom of God, Matt xiii: 31–33, it is not unnatural to understand the first, that of the mustard seed namely, as referring mainly to its extensive growth, while the other, that of the leaven hid in three measures of meal, is taken to have respect rather to this intensive growth, by which the new divine nature of christianity is required to penetrate and pervade always more and more the substance of our general human life itself, with a necessity that can never stop till the whole mass be wrought into the same complexion. It is certain at all events, that the parables together refer to both forms of increase; for the mere taking of volume outwardly is just as little sufficient of itself to complete the conception of organic growth in the world of grace, as it is notoriously to complete the same conception in the world of nature. The taking of volume must be joined in either case with a parallel progressive taking of answerable inward form. The growth of the mustard seed itself involves this two-fold process; for it consists not simply in the accumulation of size, but in the assumption at the same time of a certain type of vegetable life throughout the entire compass of its leaves and branches. It is, however, more particularly the image of leaven that serves to bring out this last side of the subject in all its force, and that might seem accordingly to be specially designed for this purpose, in distinction from all regard to the other more outward view. The parallel, as in the case of all the N. T. parables, is no mere fancy or conceit, but rests on a real analogy, by which a lower truth or fact in the sphere of nature is found to foreshadow and as it were anticipate a higher one in the sphere of the spirit. Leaven is a new force introduced into the mass of meal, different from it, and yet having with it such inward affinity that it cannot fail to become one with it, and in doing so to raise it at the same time into its own higher nature. This however comes to pass, not abruptly nor violently, but silently and gradually, and in such a way that the action of the meal itself is made to assist and carry forward the work of the leaven towards its proper end. The work thus is a process, the growing of the new principle continually more and more into the nature of the meal, till the whole is leavened. And so it is with the new order of life revealed through the gospel. Involving as it does from the start a higher form of existence for humanity as a whole (new and yet of kindred relation to the old), it is still not at once the transformation of it, in a whole and sudden way, into such higher state. It must grow itself progressively into our nature, taking this up by degrees into its own sphere and bringing out thus at the same time its own full significance and power, in order to take possession of our nature at all in any real way. In the case of the single believer accordingly it is like leaven, a power commensurate from the first with the entire mass of his being, but needing always time and development for its full actual occupation; and so also in the case of our human life as a social or moral whole. Christianity is from the very outset potentially the reconstruction or new creation of man’s universal nature (including all spheres and tracts of existence which of right belong to this idea), just as really as a deposit of leaven carries in it from the first the power of transformation for the whole mass of meal in which it has been hid; but it is like leaven again also in this respect, that the force which it has potentially needs a continuous process of inward action to gain in a real way finally its own end. There is an inner mission in its way here, which grows with as much necessity out of its relation to the world, as the mission it has to overshadow the whole earth with its branches, and which it is urged too with just as much necessity, we may add, to carry forward and fulfil. The prayer, Thy kingdom come, has regard to the one object quite as much as to the other. This comes by the depth of its entrance into the substance of humanity, as well as by the length and breadth of it, as a process of intensification no less than a process of diffusion.
And it deserves to be well considered, that these two processes are not just two different necessities, set one by the side of the other in an external way; that they are to be viewed rather as different sides only of one and the same necessity; since each enters as a condition into the fulfilment of the other, and neither can be rightly regarded without a due regard to both. The power of christianity in particular to take possession of the world extensively, depends at last on the entrance it has gained into the life of the world intensively, so far as it may have already come to prevail. And it may well be doubted, whether it can ever complete its outward mission, in the reduction of all nations to the obedience of the gospel, without at least a somewhat parallel accomplishment of its inward mission, in the actual christianization of the organic substance of humanity, to an extent far beyond all that is now presented within the bounds of the outward Church. The leaven masters the volume of the meal in which it is set, only by working itself fully into its inmost nature. The conversion of the world in the same way is to be expected, not just from the multiplication of individual converts to the christian faith, till it shall become thus of one measure with the earth, but as the result rather of an actual taking up at the same time of the living economy of the world more and more into the christian sphere. The imagination that the outward mission here may be carried through first, and the inner mission left behind as a work for future leisure, is completely preposterous. The problems then which fall to this last have a direct and most important bearing always, on the successful prosecution also of the object proposed to the first. To make the reign of Christ more deep and inward for the life of the world, is at the same time to prepare the way correspondingly for its becoming more broad and wide. The proper solution of a great theoretic question, lying at the foundation of the christian life, and drawing after it consequences that reach over nations and centuries, may be of more account for the ultimate issues of history, than the present evangelization of a whole continent like Africa. At this very time it is of more account far, that the