He went this time knowing better than his fellow royalists the meaning of events.  He was still a rank, but at least an intelligent, conspirator.  English correspondents at Rouen and Caen report him in the company of one Watson, an Independent; and that he is proposing “to join the interests of all the English papists with the bloody party that murdered the king.”  Dr. Winsted, an English doctor in Rouen, asked him with indignation how he could meditate going back to England, “considering the abomination of that country.”  Digby replied that he was forced to it.  “If he went not now he must starve.”  He plainly saw who was the real and only force in England; and he was going to make a bargain with the strong man for himself and his co-religionists.  As a matter of fact there is no trace of his return at this moment.  Not merely was his property in danger, but his head as well.  Yet he never repented of his policy, and he carried it out, so far as might be, in his dealings with Cromwell a few years later.  And Henrietta Maria bore him no grudge on this score.

Exile in Paris meant friendly intercourse with, and consolation of the Queen, but also scientific research.  In 1651 Evelyn was visiting him there, and being stirred by his enthusiasm into attending Febur’s chemistry lectures along with him.  Before that must have taken place his pilgrimage to Descartes, who died in 1650.  Apparently Sir Kenelm had gone to Egmont as an unknown stranger; and it throws light on his wide reputation as a man of ideas and a conversationalist, that into his torrent of questions and speculation Descartes broke with, “You can be none other than Digby.”  The English scientist’s practical mind—­for he had always a practical end in view, however fantastic his methods—­showed itself in his counsel to the author of the Discours sur la Methode.  Why all this labour for mere abstract speculation?  Why not apply his genius to the one great subject, the prolongation of human life?  Descartes, it appears, did not need the advice.  He said the subject was engaging his mind; and though he “dared not look forward to man being rendered immortal, he was quite certain his length of life could be made equal to the patriarch’s.”  In fact, he was composing at the time an Abrege de Medecine, and popular report said he believed men could live four or five hundred years.  He died prematurely of too much faith in his own medical theories.

In 1653 permission was given to Digby to return, on condition he would not meddle with Royalist plots.  He had been in communication with Cromwell, and had done some diplomatic business for him in Paris.  On his return in 1654, and for the next few years, he was in the closest relations with the Protector, thereby carrying out the principle he had probably adopted from White, of a “universal passive obedience to any species of government that had obtained an establishment.”  His Royalist friends made an outcry, and so did the Puritans; but Digby