His constructive theories were not easy to set up since the notion of a set could not be taken as a basic concept but had to be built up using more basic notions which, in Brouwer's case, were choice sequences.
Kanyang liwanag theories ay hindi madaling mag-set up dahil ang pagkaunawa ng isang set ay hindi kinuha bilang isang pangunahing konsepto ngunit nagkaroon na binuo up gamit ang mas basic notions kung saan, sa Brouwer ng kaso, ay pinili sequences.