What is knowledge and how does it grow as science progresses? Janina had been thinking about it for a while now.

We can represent what we know as a system of sentences. Now, you can say that a particular person has an actualized knowledge of something, when the relevant sentence is present in their mind – when it is easily recalled. The knowledge is potential when that recall takes more time, for instance when we derive a theorem of geometry which we learned at school but forgot. Our memory is not infinite; we often extend it by taking notes and accumulating books. They also store our potential knowledge. That is, as long as we have them.

August 1939 turned out very different from what it was supposed to be. The next Unity of Science congress was scheduled to start at Harvard in the first week of September and Janina was going to go to America shortly before that. She would talk about confirmation.

Janina was one of only a handful of Warsaw researchers who accepted the invitation; others were put off by the high cost of crossing the ocean. The cost of having stayed at home would soon prove to be even higher. Another one to accept the invite, Alfred Tarski, was going to depart early to give some talks before the Congress, and managed to secure a visa and a ticket. But that was in the beginning of August, and Janina wanted to leave later. By then, war was already in the air and American visas and overseas travel were out of the question. On September 1st, it was official.

Years later, Carnap would recall the beginning of the congress it in his autobiography:

In spite of the exciting world events, we found it possible to devote ourselves to the theoretical discussions of the Congress, which clearly demonstrated how strong the interest in an exact philosophy was in this country.

On September 6th, a day before her scheduled talk, instead of rehearsing her arguments and polishing off her English grammar, Janina and her husband Dolek, like thousands of other people, packed some essentials and left Warsaw to go East. It was one thing to be a resident of Warsaw as the German army was approaching. It was a whole other thing to be a Jewish resident of Warsaw with a well-known communist past. It was simply not an option to stay.

She packed a small backpack. What could have been in it? Not many clothes – she would miss first her winter, and then her summer clothes in the coming months. Probably a book or two, these people just couldn’t live without that (that same month, her friend Stanisław read Gone with the Wind while on duty as an officer). Any of her own work? Probably not, surely they were hoping to be back eventually.

They had to trek through the woods, avoiding roads and train tracks, as those would be bombarded daily. Soon enough Janina and Dolek were separated on the road. After well over a month of travel, she reached Vilnius and found her husband again, only to separate again after one day. He followed the new Soviet rule and went to the city of Białystok. She chose the semi-independent Lithuania, hoping to secure them an American visa and a future at some university. She moved into this house, and got to work.

One of the first things she did after settling in was to write that paper about knowledge. She had arrived with no notes, only with what was in her head. Less than two months later, she presented it at a seminar.

Those, however, who left all their scientific tools, i.e., notes and books, when fleeing, unprepared – they feel acutely how unreliable this replacement of knowledge with potential knowledge sometimes is. [*]

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[*] Source of the quote: Hosiasson 1948. Translation mine, but an English translation was published as well. Link to both.