Thai historians indicate that the strain on Taksin had taken a heavy toll, and that the king had started to become a religious fanatic.

Taksin shows increasing signs of mental trouble from 1781, believing himself to be a future Buddha and expecting to change the color of his blood from red to white.

He begins practicing meditation, even lecturing the monks and, at times, flogging monks who refuse to worship him.

Economic tension caused by war grows increasingly serious.

Looting and other crime is rampant as famine spreads.

Immanuel Kant writes his Critique of Pure Reason in 1781.

Considered one of the most influential works in the history of philosophy, the Critique is an investigation into the foundations and limits of human knowledge, and the extent to which the human mind is able to engage in metaphysics.

Kant builds on the work of empiricist philosophers such as John Locke and David Hume, as well as rationalists such as Gottfried Wilhelm Leibniz and Christian Wolff.

He expounds new ideas on the nature of space and time, and claims to provide solutions to Hume's skepticism regarding human knowledge of the relation of cause and effect, and René Descartes' skepticism regarding knowledge of the external world.

Kant claims to enact a 'Copernican revolution' in philosophy with his doctrine of transcendental idealism, according to which our knowledge does not "conform to objects", but rather objects "conform to our knowledge".

Knowledge independent of experience Kant calls "a priori" knowledge, while knowledge obtained through experience is termed "a posteriori".

According to Kant, a proposition is a priori if it is necessary and universal.

A proposition is necessary if it could not possibly be false, and so cannot be denied without contradiction.

A proposition is universal if it is true in all cases, and so does not admit of any exceptions. Knowledge gained a posteriori through the senses, Kant argues, never imparts absolute necessity and universality, because it is always possible that we might encounter an exception.

According to Kant's doctrine, the human mind shapes and structures the world of experience, making knowledge possible.

Kant claims to have discovered another attribute of propositions: the distinction between "analytic" and "synthetic" judgments.

According to Kant, a proposition is analytic if the content of the predicate-concept of the proposition is already contained within the subject-concept of that proposition.

For example, Kant considers the proposition "All bodies are extended" analytic, since the predicate-concept ('extended') is already contained within—or "thought in"—the subject-concept of the sentence ('body').

The distinctive character of analytic judgements was therefore that they can be known to be true simply by an analysis of the concepts contained in them; they are true by definition.

In synthetic propositions, on the other hand, the predicate-concept is not already contained within the subject-concept.

For example, Kant considers the proposition "All bodies are heavy" synthetic, since the concept 'body' does not already contain within it the concept 'weight'.

Synthetic judgments therefore add something to a concept, whereas analytic judgments only explain what is already contained in the concept.

Prior to Kant, it was thought that all a priori knowledge must be analytic.

Kant, however, argues that our knowledge of mathematics, of the first principles of natural science, and of metaphysics, is both a priori and synthetic.

The peculiar nature of this knowledge, Kant argues, cries out for explanation.

The central problem of the Critique is therefore to answer the question: "How are synthetic a priori judgements possible?"

It is a "matter of life and death" to metaphysics and to human reason, Kant argues, that the grounds of this kind of knowledge be explained.

Swedish chemist Carl Wilhelm Scheele, analyzing the calcium tungstate mineral now known as scheelite, identifies lime and an acid that he calls tungstic acid in 1781.

His compatriot Torbern Olaf Bergman concludes that a new metal (now known to be tungsten) can be prepared from the acid.

Louis XV had decided in 1772 to make Madame du Barry, with whom he was infatuated, a special gift at the estimated cost of 2,000,000 livres.

He had requested that Parisian jewelers Boehmer and Bassenge create a diamond necklace which would surpass all others in grandeur.

It has taken the jewelers several years and a great deal of money to amass an appropriate set of diamonds.

In the meantime, Louis XV has died of smallpox, and du Barry had been banished from court by his successor.

The necklace consists of many large diamonds arranged in an elaborate design of festoons, pendants and tassels.

The jewelers hope it can be a product that the new Queen of France, Marie Antoinette, can buy and indeed in 1778 the new king, Louis XVI, had offered it to his wife as a present, but she had refused.

According to Madame Campan, a French educator and royal lady-in-waiting, the Queen had refused it with the statement that the money would be better spent equipping a man-of-war.

Some said that Marie Antoinette refused the necklace because she did not want to wear any jewel which had been designed for another woman, especially if that woman was a courtesan disliked by the Queen.

According to others, Louis XVI himself had changed his mind.

After having vainly trying to place the necklace outside of France, the jewelers again attempt to sell it to Marie Antoinette after the birth of the dauphin Louis-Joseph in 1781.

The Queen again refuses.

Joseph Priestly obtains water by igniting the gas now known to be hydrogen in oxygen in 1781; improvements by the English theologian and scientist in the manipulation of gases have enabled him to investigate the properties of phlogiston.

French chemist Antoine-Laurent Lavoisier, repeating the experiments of English chemist and physicist Henry Cavendish, coins the word hydrogéne for the gas.

Quickly accepted by the scientific community, the element's name combines Greek hydro, water, with gen, bearing or forming.