Whilst the greatest effort has been made to ensure the quality of this text, due to the historical nature of this content, in some rare cases there may be minor issues with legibility. Whilst the conception of Leonardo as a thinker, discoverer and scientist has thus been very greatly expanded, modern art-research has been compelled to narrow the compass of his artistic work. More than half of what, a generation ago, was regarded as the authentic work of Leonardo, has gradually been pronounced to be that of others; on the other hand, attempts that have been made to replace what is lost by attributing other works to him, must, on the whole, be characterised as failures.