The parable of the sower is much denser than it appears. It is a treatise of sorts on the spiritual life.
The main variable obviously is the soil itself. In the first instance we have seed scattered onto a footpath. Terrain that is traveled upon becomes packed down and hard. Here the seed of God’s word cannot gain entry. This soil is not receptive, perhaps not even vaguely aware. A good analogy might be somebody young who lives according to the flesh. They live in the world of their senses and have little use for the realm of the spirit. It is little wonder that Satan so easily swoops in to render the seed even more remote. It matters little, for if this soil is not broken up and repurposed, no seed would ever penetrate, much less take root.
Next comes the rocky soil. This instance is deceptively complex. In this case the sun represents tribulations and persecutions, or in other words, the world. The seed penetrates this soil, but the rocks give very little room for the seed to develop a root (prayer). Therefore the seed jumps out into growth mode too early (activism). But without the root of prayer, the seedling does not have access to the resources necessary to use the sun of tribulation for the purposes of growth. Now what should been the power supply for growth has become the source of a bitter enfeeblement. So while the seed made it safely into the soil before the bird could take it away, not having been able to choose the better part, the seed does not fully develop and fails to produce fruit. The rocks in the soil must be removed. The footpath may very well have had rocks within, but they were not relevant. Here their detrimental effect is revealed. The soil had big impediments to long-lasting sustainable growth due to it not allowing the inner life to develop to such a degree that the outer life in the world could withstand challenges and pressures and still survive.
The third instance is where the soil is both receptive enough to avoid the plunder of the bird as well as free from impediments to reaching the deeper resources and growing a deep root. In fact this soil is so good for growth that many things take up root here. Unfortunately they are not all good, and the soil cannot support them all equally. The thorns, unlike the bird, do not prevent the seed from gaining initial access. Similarly, the thorns do not prevent the growth of a root, which the rocks had done. So the seed has a good root by which to access the resources it needs to withstand the sun and use it for growth, but sadly it must compete with many voracious and debilitating thorns, and thus comes to ruin even though the conditions of the soil were theoretically ready to support growth to maturity. Sadly, the lure of riches stole the resources of this healthy soil and depleted the seedling of its needed energies for growth and fruitfulness.
The soul will need to undergo tilling to deaden the desires of the flesh that make it easy prey for the Enemy. Then the soul needs to undergo the removal of the rocks that discourage the primacy of the inner life and leave only the option for a superficial and anemic life of prayer with an unfueled involvement in the world that ultimately runs empty at the first sign of trouble. Lastly, the soul needs to be purified and refined of all that would compete with and steal strength from the soul on its journey to abundant spiritual fruitfulness.