(2)  No person shall be convicted of any offence referred to in section 4(1)(c) or (d) if such person proves that the publication in respect of which he is charged was printed, published, sold, offered for sale, distributed, reproduced or imported (as the case may be) without his authority, consent and knowledge and without any want of due care or caution on his part or that he did not know and had no reason to believe that the publication had a seditious tendency.