Plato Timaeus 90

We have frequently asserted ¹ that there are housed within us in three regions three kinds of soul, and that each of these has its own motions; so now likewise we must repeat, as briefly as possible, that the kind which remains in idleness and stays with its own motions; in repose necessarily becomes weakest, whereas the kind which exercises itself becomes strongest; 90a wherefore care must be taken that they have their motions relatively to one another in due proportion. And as regards the most lordly kind of our soul, we must conceive of it in this wise: we declare that God has given to each of us, as his daemon, ² that kind of soul which is housed in the top of our body and which raises us—seeing that we are not an earthly but a heavenly plant up from earth towards our kindred in the heaven. And herein we speak most truly; for it is by suspending our head and root from that region whence the substance of our soul first came that the Divine Power 90b keeps upright our whole body.
  Whoso, then, indulges in lusts or in contentions and devotes himself overmuch thereto must of necessity be filled with opinions that are wholly mortal, and altogether, so far as it is possible to become mortal, fall not short of this in even a small degree, inasmuch as he has made great his mortal part. But he who has seriously devoted himself to learning and to true thoughts, and has exercised these qualities above all his others, 90c must necessarily and inevitably think thoughts that are immortal and divine, if so be that he lays hold on truth, and in so far as it is possible for human nature to partake of immortality, ³ he must fall short thereof in no degree; and inasmuch as he is for ever tending his divine part and duly magnifying that daemon who dwells along with him, he must be supremely blessed. ⁴ And the way of tendance of every part by every man is one—namely, to supply each with its own congenial food and motion; and for the divine part within us the congenial motions 90d are the intellections and revolutions of the Universe. ⁵ These each one of us should follow, rectifying the revolutions within our head, which were distorted at our birth, by learning the harmonies and revolutions of the Universe, and thereby making the part that thinks like unto the object of its thought, in accordance with its original nature, and having achieved this likeness attain finally to that goal of life which is set before men by the gods as the most good both for the present and for the time to come. 90e
  And now the task prescribed for us at the beginning to give a description of the Universe up to the production of mankind, would appear to be wellnigh completed. For as regards the mode in which the rest of living creatures have been produced we must make but a brief statement, seeing that there is no need to speak at length; for by such brevity we will feel ourselves to be preserving a right proportion in our handling of these subjects. Wherefore let this matter be treated as follows.