J.S.Mill, On liberty (1859).

Chapter I : Introductory

... there is also in the world at large an increasing inclination to stretch unduly the powers of society over the individual, both by the force of opinion and even by that of legislation: and as the tendency of all the changes taking place in the world is to strengthen society, and diminish the power of the individual, this encroachment is not one of the evils which tend spontaneously to disappear, but, on the contrary, to grow more and more formidable. The disposition of mankind, whether as rulers or as fellow-citizens, to impose their own opinions and inclinations as a rule of conduct on others, is so energetically supported by some of the best and by some of the worst feelings incident to human nature, that it is hardly ever kept under restraint by anything but want of power; and as the power is not declining, but growing, unless a strong barrier of moral conviction can be raised against the mischief, we must expect, in the present circumstances of the world, to see it increase.

Chapter IV: On the limits to the authority of society over the individual

In the conduct of human beings towards one another, it is necessary that general rules should for the most part be observed, in order that people may know what they have to expect; but in each person's own concerns, his individual spontaneity is entitled to free exercise.

http://www.bartleby.com/130/

On liberty concerning one’s life

Lucretius (99-55 bc), De rerum natura, Bk. 3

Then, too, Democritus, when ripened eld
Admonished him his memory waned away,
Of own accord offered his head to death.
Even Epicurus went, his light of life
Run out, the man in genius who o'er-topped
The human race, extinguishing all others,
As sun, in ether arisen, all the stars.
Wilt thou, then, dally, thou complain to go?-
...

And too, when all is said,

What evil lust of life is this so great

Subdues us to live, so dreadfully distraught

In perils and alarms?

http://www.intratext.com/IXT/ENG1332/_P3.HTM

dopoché matura vecchiezza fece sentire a Democrito

che i memori movimenti della mente languivano,

spontaneamente alla morte andò incontro e offrì il proprio capo.

Lo stesso Epicuro morì, dopo aver percorso il luminoso tratto

della vita, egli che per ingegno superò il genere umano, e tutti

offuscò, come il sole sorto nell'etere offusca le stelle.

E tu esiterai e t'indignerai di morire?

...

Infine, a trepidare tanto nei dubbiosi cimenti

quale trista brama di vita con tanta forza ci costringe?

http://spazioinwind.libero.it/latinovivo/Testintegrali/lucr3trad.htm

On liberty and dignity of ending one’s life: Eluana Englaro