Below is an extract from Nostradamus's own introduction to his prophetic writings:

Thy late coming hath caused me to bestow much time in continual and nocturnal watchings, that I might leave a memorial of me after my death, to the common benifit of mankind, concerning the things which the Divine Essence hath revealed to me. Since it hath pleased the Immortal God that thou art come late and art incapable to receive into thy weak understanding what I am forced to define of futurity; since it is not possible to leave thee in writing what might be obliterated by the injury of time, for the hereditary gift of occult prediction shall be locked up in my breast; considering also that events are definitely uncertain, and that all is governed by the power of God, who inspired us.

  

Although I have foretold long before what hath afterwards come to pass, and in particular regions, acknowledging all to have been done in divine virtue and inspiration, I was willing to hold my peace by reason of the injury - not only of the present time, but also of the future - because to put them in writing, the Kingdoms, Sects, and Religions shall be so drametrically opposed, that if I should relate what shall happen hereafter, those of the present Reign, Sect, Religion and Faith, would find it so disagreeing

with their fancies, that they would comdemn that which future ages shall find and know to be true. Consider the sayings of our Saviour..

For this reason I have withheld my tongue from the vulgar, and my pen from paper. But, afterwards, I was willing for the common good to enlarge myself in dark and abstruse sentences, declaring the future events.

  

I say, therefore, that you may understand me well, because the knowledge of this matter cannot yet be imprinted in thy weak brain. Future causes afar off are subject to the knowledge of human creatures, if things present and future were neither obscure nor hidden from the intellectual seal; but the perfect knowledge of the cause of things cannot be aquired without the divine inspiration, seeing that all prophetical inspiration received hath its original principle from God the Creator, and from nature; for the understanding being intellectually created cannot see occult things, unless it be by the means of the thin flame, to which the knowledge of future causes is inclined.

As for us, who are but men, we cannot attain anything by our natural knowledge of God our Creator. But I speak to thee a little too obscurely. There are secrets that are received by the subtle spirit of fire, by which the understanding is moved to contemplate the highest celestial bodies, being active and vigilant to the very pronunciation without fear or any shameful loquacity; all of which proceeded from the divine power of the Eternal God, from whom all goodness flows; for the secrets of God are incomprehensible, and their efficient power is far remote from the natural knowledge,m taking there origin in the free will, causing those things to appear which otherwise could not be known, neither by human auguries nor by any hidden knowledge or secret virtue under Heaven, but only by the means of some invisible eternal being."