Above all, the search after truth and its eager pursuit are peculiar to man. And so, when we have leisure from the demands of business cares, we are eager to see, to hear, to learn something new, and we esteem a desire to know the secrets or wonders of creation as indispensable to a happy life. Thus we come to understand that what is true, simple, and genuine appeals most strongly to a man’s nature.

[In primisque hominis est propria veri inquisitio atque investigatio. Itaque cum sumus necessariis negotiis curisque vacui, tum avemus aliquid videre, audire, addiscere cognitionemque rerum aut occultarum aut admirabilium ad beate vivendum necessarian! ducimus. Ex quo intellegitur, quod verum, simplex sincerumque sit, id esse naturae hominis aptissimum.]

Marcus Tullius Cicero (106-43 BC) Roman orator, statesman, philosopher
De Officiis [On Duties; On Moral Duty; The Offices], Book 1, ch. 4 / sec. 13 (44 BC) [tr. Miller (1913)]
    (Source)

Original Latin. Alt. trans.:

But of all the properties and inclinations of men, there is none more natural and peculiar to them than an earnest desire and search after truth. Hence it is that our minds are no sooner free from the thoughts and engagements of necessary business, but we presently long to be either seeing, or hearing, or learning of something; and esteem the knowledge of things secret and wonderful as a necessary ingredient of a happy life. Whence it appears that nothing is more agreeable and suited to the nature and minds of men than undisguised openness, truth, and sincerity.
[tr. Cockman (1699)]

The desire and investigation of truth is proper to man. When disengaged from necessary business and cares, we are eager to add to our knowledge by examining for ourselves or listening to others. The discovery of what is secret or wonderful, we are disposed to conceive essential to happiness. Hence, what is true, simple, and undisguised, is best adapted to human nature.
[tr. McCartney (1798)]

The distinguishing property of man is to search for and to follow after truth. Therefore, when relaxed from our necessary cares and concerns, we then covet to see, to hear, and to learn somewhat; and we esteem knowledge of things either obscure or wonderful to be the indispensable means of living happily. From this we understand that truth, simplicity, and candour, are most agreeable to the nature of mankind.
[tr. Edmonds (1865)]

The research and investigation of truth, also, are a special property of man. Thus, when we are free from necessary occupations, we want to see, or hear, or learn something, and regard the knowledge of things either secret or wonderful as essential to our living happily and well.
[tr. Peabody (1883)]