“Logic is the foundation of the certainty of all the knowledge we acquire.”
“If in other sciences we should arrive at certainty without doubt and truth without error, it behooves us to place the foundations of knowledge in mathematics...”
“We confess knowledge without certainty, truth without objectivity.”
“As we acquire knowledge, things do not become more comprehensible, but more mysterious.”
“All the knowledge I possess everyone else can acquire, but my heart is all my own.”
“To acquire knowledge, one must study;but to acquire wisdom, one must observe.”