The same noble spirit pervades his 'Nathan the Wise,' which he wrote about this time as a relief to his controversial discussions, and as another protest against the narrow-minded assumptions of the professional theologians. Lessing had ever contended that the stage might prove as useful a pulpit as the church, and in 'Nathan' he strove to preach the universal brotherhood of mankind; its hero is a Jew of ideal and pure morality. The whole purpose of the drama was a stricture on class prejudices and an enunciation of the innate truth that underlies all forms of creeds. The play is too well known even in this country to require much comment; it is a noble monument of toleration and large-mindedness, and the fact that he could produce it under the load of a crushing sorrow speaks volumes for the true earnest religious faith that dwelt in Lessing's nature. At the time its pure tendencies were not understood. Lessing had progressed beyond the comprehension of his age, and the inevitable consequences ensued,--misconstruction and mental loneliness. He began to be regarded with suspicion as a dangerous innovator; even old friends held aloof in doubt. Meanwhile his only comfort remained in his home, in the step-children, whom his wife had brought thither. His step-daughter was his tender and attentive companion, for since his wife's death Lessing's health had declined, and he required care. Though no trace of impaired vigour appears in his writings of the period, which indeed are animated by an exhilarating vitality, yet too evident traces of impaired vigour appeared in himself. He grew languid, an excessive inclination to sleep overpowered him; he suffered from attacks of vertigo. Yet as long as he could hold a pen he should write, he told his brother,--write in the cause of what he firmly held to be the truth.
A small pamphlet, consisting of a hundred propositions, entitled 'The Education of the Human Race,' was his next production, a work pregnant with thought that opens out wide vistas of knowledge and progress to mankind. Lessing indeed was the first man of his century to formulate the modern doctrine of progress; he preached a true millennium of toleration, love, and knowledge; he distinctly proclaimed his faith in the immortality of the soul. 'The Education of the Human Race' is a splendid disavowal of his enemies' calumnious assertions. It was a glorious swan-song, wherewith he lulled himself into eternal peace.