I. (2) To speak in a manner intelligible to the multitude, and to
comply with every general custom that does not hinder the
attainment of our purpose. (3) For we can gain from the multitude
no small advantages, provided that we strive to accommodate
ourselves to its understanding as far as possible: moreover,
we shall in this way gain a friendly audience for the reception
of the truth.
II. (17:4) To indulge ourselves with pleasures only in so far as they
are necessary for preserving health.
III. (5) Lastly, to endeavor to obtain only sufficient money or other
commodities to enable us to preserve our life and health, and to
follow such general customs as are consistent with our purpose.

[18] (1) Having laid down these preliminary rules, I will betake
myself to the first and most important task, namely, the amendment
of the understanding, and the rendering it capable of understanding
things in the manner necessary for attaining our end. (2) In order
to bring this about, the natural order demands that I should here
recapitulate all the modes of perception, which I have hitherto
employed for affirming or denying anything with certainty, so that
I may choose the best, and at the same time begin to know my own
powers and the nature which I wish to perfect.

[19] (1) Reflection shows that all modes of perception or knowledge
may be reduced to four:-
I. (2) Perception arising from hearsay or from some sign which
everyone may name as he please.
II. (3) Perception arising from mere experience - that is, form
experience not yet classified by the intellect, and only so called
because the given event has happened to take place, and we have no