Expressing the inimitable tranquillity of the Stoic sage, Seneca declares that

Perhaps one of Stoicism's greatest points of appeal, prominent in its resurgence in the early modern period, is its assertion that happiness is attainable by any rational individual. Moreover, this happiness is, as Seneca depicts it, a this-worldly salvation: the rational individual can aspire to a perfect happiness, a tranquillity impervious to any and all assaults of Fortune. Such is the virtue of Stoic ethics famously celebrated in the sixteenth century by Justus Lipsius, who, exasperated by the conflicts raging within the Christian tradition and the horrific wars accompanying them, looked to Stoicism for an alternate source of moral sustenance and the prospect of genuine respite from public tumult – to be sure, nothing less than an enduring peace of mind. According to the Stoic model, such eminent tranquillity, which entails perfecting one's intellect, is founded on a specific collection of doctrines: an immanentist theology whereby God and the universe are rational in nature and can be perfectly apprehended by the human mind; virtue that is readily indicated in natural impulse; a diagnosis of the passions, the primary obstacle to virtue, in terms that immediately invoke their susceptibility to remedy; and, finally, psychotherapy as the means to happiness, a means that is subject to individual agency and responsibility.