The document discusses the contributions of Israel Kirzner to entrepreneurship theory, particularly differentiating between two conceptualizations of his work: Kirzner Mark I focuses on alertness to existing arbitrage opportunities in a single time period, while Kirzner Mark II incorporates multiple time periods and emphasizes creativity amid uncertainty. Both perspectives highlight the role of entrepreneurial alertness but illustrate distinct nuances in understanding opportunities and their subjective nature. The document further explores the implications of these concepts within the Austrian economics tradition and their potential as a foundation for empirical research.