Date: 1684

"For certainly there must be some change in our mind when we have some thoughts and then others, and, in fact, ideas of things we are not actually thinking about are in our minds as the shape of Hercules is in rough marble."

— Leibniz, Gottfried Wilhelm (1646-1716)

Date: w. 1628, published in 1684, 1701

"The writers displayed many geometrical truths before my very eyes, as it were, and derived them by means of logical arguments"

— Descartes, René (1596-1650)

Date: w. 1628, published in 1684, 1701

"This is similar to the way in which we know that the last link in a long chain is connected to the first: even if we cannot take in at one glance all the intermediate links on which the connection depends, we can have knowledge of the connection provided we survey the links one after the other, ...

— Descartes, René (1596-1650)

Date: w. 1628, published in 1684, 1701

"For the human mind has within it a sort of spark of the divine, in which the first seeds of useful ways of thinking are sown, seeds which, however neglected and stifled by studies which impede them, often bear fruit of their own accord."

— Descartes, René (1596-1650)

Date: w. 1628, published in 1684, 1701

"But since it is not easy to review all the connections together, and moreover, since our task is not so much to retain them in our memory as to distinguish them with, as it were, the sharp edge of our mind, we must seek a means of developing our intelligence in such a way that we can discern the...

— Descartes, René (1596-1650)

Date: w. 1628, published in 1684, 1701

"We can best learn how mental intuition is to be employed by comparing it with ordinary vision."

— Descartes, René (1596-1650)

Date: w. 1628, published in 1684, 1701

"Even though problems such as these can often be solved without a method and can sometimes perhaps be solved more quickly through good luck than through method, nevertheless they might dim the light of the mind and make it become so habituated to childish and futile pursuits that thereafter it wo...

— Descartes, René (1596-1650)

Date: w. 1628, published in 1684, 1701

"First, in so far as our external senses are all parts of the body, sense-perception, strictly speaking, is merely passive, even though our application of the senses to objects involves action, viz. local motion; sense-perception occurs in the same way in which wax takes on an impression from a s...

— Descartes, René (1596-1650)

Date: w. 1628, published in 1684, 1701

"Thirdly, the 'common' sense functions like a seal, fashioning in the phantasy or imagination, as if in wax, the same figures or ideas which come, pure and without body, from the external senses."

— Descartes, René (1596-1650)

Date: w. 1628, published in 1684, 1701

"Again, the pen as a whole does not move in exactly the same way as its lower end; on the contrary, the upper part of the pen seems to have a quite different and opposite movement. This enables us to understand how all the movements of other animals can come about, even though we refuse to allow ...

— Descartes, René (1596-1650)