Latin text and English translation of the reported quotations
  from On the Nature of Things (De Rerum Natura) 
by Titus Lucretius Caro (~60 b.C.)
Latin text

[Denique] si semper motus conectitur omnis
et vetere exoritur novus ordine certo
nec declinando faciunt primordia motus principium quoddam quod fati foedera rumpat,
ex infinito ne causam causa sequatur,
libera per terras unde haec animantibus extat,
unde est haec, inquam,  fatis avulsa voluntas
per quam progredimur quo ducit quemque voluptas,
declinamus item motus nec tempore certo
nec regione loci certa, sed ubi tulit mens?
[II, 251-260].
....
Quare in seminibus quoque idem fateare necessest,
esse aliam praeter plagas et pondera causam
motibus, unde haec est nobis innata potestas,
de nilo quoniam fieri nil posse videmus.
Pondus enim prohibet ne plagis omnia fiant
externa qua vi. Sed ne mens ipsa necessum
intestinum habeat cunctis in rebus agendis
et devicta quasi cogatur ferre patique,
id facit exiguum clinamen principiorum
nec regione loci certa nec tempore certo
[II, 284-293].
English translation

[Then,] if all motions are ever co-linked and the new ever arises from the old in fixed order; if the fundamental entities are not deviated by some principle of motion which violates the impositions of destiny - thus disarranging the endless succession of causes; where is it springing from this animals' power of moving freely over the lands? Where - I wonder - does it come this free will wrested from the fates, in virtue of which we step where we like more, without deviating our motion neither at some fixed instant, nor at some fixed place, but where our minds bring us?
.... Therefore, we must admit that, on the seeds of  matter, besides shocks and gravity, another factor of motion also acts, upon which such of our innate powers depends, since nothing can come from nothing. Gravity, indeed, prohibits that everything occurs by shocks, as by external actions. But, if in every decision the mind itself does not follow an inner necessity, nor, as tamed, it is compelled to bear and suffer, this fact depends upon those small deviations of elementary particles, which occur at uncertain times and places.
(Translated by the Author)