Superscript numbers in the translation refer to similarly numbered notes in the Commentary

THE FIRST BOOK OF THE OPTICS

OF ABŪ 'ALĪ AL-ḤASAN IBN AL-ḤASAN IBN AL-HAYTHAM

THE CHAPTERS OF THIS BOOK WHICH ARE EIGHT

I 1b

Chapter 1: Preface to the whole book
Chapter 2: Inquiry into the properties of sight
Chapter 3: Inquiry into the properties of lights and into the manner of radiation of lights
Chapter 4: On the effect of light upon sight
Chapter 5: On the structure of the eye
Chapter 6: On the manner of vision
Chapter 7: On the utilities of the instruments of sight
Chapter 8: On the reasons for the conditions without the combination of which vision is not effected

CHAPTER I

PREFACE TO THE WHOLE BOOK

I 2a

[1] Early investigators diligently pursued the inquiry into the manner of visual sensation and applied their thoughts and effort to it, eventually reaching the limit to which their investigation had led, and gaining as much knowledge of this matter as their inquiry and judgement had yielded. Nevertheless, their views on the nature of vision are divergent and their doctrines regarding the manner of sensation not concordant. Thus, perplexity prevails, certainty is hard to come by, and there is no assurance of attaining the object of inquiry. How strong, in addition to all this, is the excuse for the truth to be confused, and how manifest is the proof that certainty is difficult to achieve! For the truths are obscure, the ends hidden, the doubts manifold, the minds turbid, the reasonings various; the premisses are gleaned from the senses, and the senses (which are our tools) are not immune from error. The path of investigation is therefore obliterated and the inquirer, however diligent, is not infallible. Consequently, when inquiry concerns subtle matters, perplexity